The Mummy's Club

New weight advice for pregnancy

Admin — Fri, 30 Jul 2010 12:19:51 +0000

Many newspapers have reported on new official guidelines for how women can manage their weight before, during and after pregnancy. The advice comes from the National Institute for Health and Clinical Excellence (NICE).

The importance of the guidelines is borne out by figures suggesting that more pregnant women than ever are overweight or obese. The Guardian suggests that, “15-20% of women getting pregnant are overweight or obese”. The Daily Mail puts the number higher, saying that “almost half of expectant mothers are overweight or obese”. It goes on to spell out the dangers of being obese or overweight during pregnancy, which include “fatal health conditions such as blood clots, pre-eclampsia, miscarriages and stillbirths”.

The newspapers also dispel the myth that women should eat for two during pregnancy. Further advice reported in the press includes taking at least 30 minutes of moderate exercise per day during pregnancy, and that pregnant women should avoid dieting and only need to have an extra 200 calories a day in the last three months of their pregnancy.

These guidelines are published by NICE, and are evidence-based. They are designed so that doctors can give women up-to-date reliable advice to follow to maintain a healthy weight before, during and after their pregnancy.

Where did the advice come from?

The advice has just been published by the National Institute for Health and Clinical Excellence (NICE) as part of its public health programme. NICE produces guidance on the promotion of good health and the prevention of ill health for those working in the NHS, local authorities and the wider public and voluntary sector.

What are the health risks of being obese during pregnancy?

Women who are obese (with a BMI over 30) when they become pregnant face an increased risk of complications such as diabetes, miscarriage, pre-eclampsia, blood clots and death. Obese women are also more likely to have an induced or longer labour, post-delivery bleeding and slower wound healing after delivery. They also tend to be less mobile, which can result in a need for more pain-relieving drugs during labour. These can be difficult to administer in obese women, resulting in a greater need for general anaesthesia with its associated risks.

For women who have gained weight between pregnancies, even a relatively small gain of 1-2 BMI units can increase the risk of high blood pressure or diabetes during their next pregnancy and may also increase the chance of giving birth to a large baby.

What sort of diet does NICE recommend?

NICE offers the following dietary advice to help women to achieve and maintain a healthy weight:

Base meals on starchy foods (such as potatoes, bread, rice and pasta), choosing wholegrain where possible.
Eat foods rich in fibre.
Eat at least five portions of fruit and vegetables per day in place of foods higher in fat or calories.
Eat as little as possible of fried foods, and drinks and confectionery high in sugars and fats.
Eat breakfast.
Watch portion size of meals and how often they are eaten.

What should women aim to weigh before getting pregnant?

Women with a BMI of 30 or more can achieve significant health benefits if they lose between 5-10% of their weight. Further weight loss to achieve a BMI within the healthy range of 18.5 and 24.9 is encouraged.

What about weight during pregnancy?

The amount of weight a woman may gain in pregnancy varies a great deal, and only some of it is due to increased body fat. The unborn child, placenta, amniotic fluid and increases in maternal blood and fluid volume all contribute to weight gain during pregnancy.

Dieting during pregnancy is not recommended as it may harm the health of the child.
There is no need to ‘eat for two’ or drink full-fat milk (as opposed to lower-fat milk). Energy needs do not change in the first six months of pregnancy. Only in the last three months do a woman’s energy needs increase by around 200 calories per day.
Moderate-intensity physical activity will not harm the mother or baby. At least 30 minutes per day of moderate intensity activity is recommended. This can include activities such as swimming or brisk walking. If women have not exercised routinely up to that point, they should begin with no more than three 15-minute sessions a week, increasing gradually to daily 30-minute sessions.
There are no formal evidence-based guidelines from the UK Government or professional bodies on what constitutes appropriate weight gain during pregnancy.

How do I safely lose weight after giving birth?

Women are encouraged to breastfeed, but are advised against dieting while breastfeeding. Women who feed their babies with breastmilk only for the first six months may require an additional 330 calories a day, but this may differ between individuals, and some of these additional calories will be derived from fat stores built up during pregnancy.

If the pregnancy and delivery are uncomplicated, mothers may start a mild exercise programme consisting of walking, pelvic floor exercises and stretching immediately after giving birth, but women should not resume high-impact activity too soon. Women who have had complicated deliveries or caesareans should not resume pre-pregnancy levels of physical activity before consulting their medical caregiver.

Health professionals should be able to provide details of appropriate community-based services for women who want support to lose weight.

Where can I get more information?

Women should consult their GP or midwife about maintaining a healthy lifestyle before, after and during their pregnancy.

Links To The Headlines

Mothers must lose baby weight before getting pregnant again, NICE says. The Daily Telegraph, July 28 2010

Weight, exercise and pregnancy confusion. BBC News, July 28 2010

Mothers who lose weight before further pregnancy ‘reduce risks’. The Guardian, July 28 2010

Don’t eat for two, pregnant mothers are told amid obesity fears. Daily Mail, July 28 2010

Early trial for autism voice test

Admin — Thu, 22 Jul 2010 16:08:50 +0000

Voice technology “could help detect autism”, BBC News has reported. The BBC website said that a new US study found that the early speech of 86% of infants with autism differed from that of unaffected children.

In the study researchers recorded the speech of three groups of children aged 10-48 months: 106 ‘typically-developing’ young children, 49 children with language delay and 77 children diagnosed with autism. Their fully automated recording devices were able to determine differences in speech between the groups and accurately predict which children were from each group. The technique also follows the child in their natural home setting, providing the opportunity for efficient and effective speech assessment in a familiar environment.

This research is still in the early stages, and further study will determine how this system could work alongside other developmental assessment methods. So far, the system has not been investigated as a method for diagnosing new cases of language or developmental delay. Before it is introduced into practice, the uses and feasibility of this novel approach will need to be explored.

Where did the story come from?

The study was carried out by researchers from the Universities of Memphis, Chicago and Kansas and was funded by the Plough Foundation at the University of Memphis. It was published in the peer-reviewed scientific journal Proceedings of the National Academy of Sciences USA.

What kind of research was this?

This was an observational study that attempted to further the techniques used in researching speech and language development. The aim was to investigate an automated method for assessing young children’s speech development on a large scale by carrying out extended recordings in the homes of infants and young children. The main goal of the research was to isolate each child’s vocalisations from other voices and background noise on candid recordings and automatically identify significant features that could be useful predictors of the child’s developmental level.

What did the research involve?

To gather audio samples, the researchers provided parents with a battery-powered recorder that was then attached to their child’s clothing, recording the child in their natural environment all day. The children recorded were drawn from three different groups: those whose parents self-reported them to be typically-developing, those reported to have language delay and those reported to have autism.

Language delay was confirmed by checking for documentation in medical records or by assessment with a speech and language clinician, and autism was confirmed by checking medical records of the diagnosis. The final sample recorded featured a total of 232 children:

106 ‘typically-developing’ children aged 10-48 months
49 children with language delay aged 10-44 months
77 children with autism aged 16-48 months

The researchers carried out a total of 1,486 all-day recordings across the groups over the three years of the study, which provided a total of 23,716 hours of audio and captured a total of 3.1 million child utterances.

The recording devices were able reliably to differentiate between the child’s vocalisations and other sounds, allowing the researchers to carry out an in-depth analysis of the 12 parameters of speech known to have a role in speech development. These parameters included how the child was able to articulate each syllable, speech rhythm, pitch, their vocal characteristics and duration of speech.

The researchers looked at the relationship between a child’s overall vocalisations and the number of the 12 parameters that were as expected according to their age.

What were the basic results?

The researchers found that the automated analysis was able to predict development.

In the typically-developing group all 12 of the parameters of speech were as expected according to their age.
In the language-delayed group 7 of 12 parameters were as expected for their age.
In the autism group few of the 12 parameters of speech were as expected according to age.

The study also found that in the typically-developing group certain vocal tendencies diminished with age, while this was not seen in the other groups. They also noted that children with autism tended to have quite unpredictable patterns of development, suggesting that they had different vocalisation from both typically-developing children and those with language delay.

Overall, the test correctly identified 90% of children who were in the ‘typically-developing’ group, 80% of those with autism and 62% of those with language delay.

How did the researchers interpret the results?

The researchers considered this research to be a ‘proof of concept’, a type of developmental project designed to test how well a conceptual method translates into real-world use. They demonstrated that their method of automated assessment was able to track children’s development on acoustic parameters known to play key roles in speech, and was also able to differentiate the vocalisations of children with autism or language delay from those of typically-developing children.

They conclude that their study of ‘automated analysis’ has the potential to advance research in speech and language development.

Conclusion

This was valuable research that has carried out extensive all-day recordings of children and found that the automated analyses of their vocalisations could distinguish between children with normal development, language delay and autism.

The advantage of this method is that it is completely automated, requiring no human intervention. As it follows the child in their home, it provides the opportunity for efficient and effective speech assessment in a familiar environment.

This research is still in the developmental stages. Further study will be needed to see how this recording system could supplement developmental assessment of children by health professionals and the standard screening and diagnostic procedures used.

So far, the system has only been used to detect previously-diagnosed conditions, and has not yet been tested as a means of identifying undiagnosed linguistic or developmental delay. This means the accuracy of the test needs further testing. Additionally, there are likely to be many other considerations to be addressed before this could be brought into practice, including the costs and feasibility of distributing recorders on a large scale and then having trained personnel available to interpret the data from these in-depth recordings.

As the researchers say, the ability to study linguistic development in natural home environments could provide a completely objective way of detecting speech-related disorders in early childhood. Such an advance would be a highly valuable medical tool for speech and language therapists.

Links To The Headlines

Autism detected in voice of children. The Daily Telegraph, July 20 2010

Speech pattern can give early clue to autism. The Independent, July 20 2010

Voice technology ‘could help detect autism’. BBC News, July 20 2010

Links To Science

Ollera DK, Niyogic P, Gray S et al. Automated vocal analysis of naturalistic recordings from children with autism, language delay, and typical development. PNAS, July 20 2010

Births at night examined

Admin — Sun, 18 Jul 2010 17:38:22 +0000

Babies born at night are “three times more at risk of death,” said the Daily Mail. The newspaper suggested that a lack of senior staff available outside of normal working hours is putting newborns at risk.

The well-conducted study behind the story reviewed records of over one million full-term, single baby births in Scotland from 1985 to 2004. It found an increased risk of newborn death out of hours (i.e. during the night time and weekends), with deaths mostly related to lack of oxygen during delivery. However, these results must be interpreted in the correct context, as the risk of newborn death was very low in both groups: 4.2 out of 10,000 births in normal working hours, and 5.6 out 10,000 births out of hours.

As the researchers say, the observations could be due to many different causes, as the reasons behind this relationship were not examined and should not be assumed to be due to ‘hospital staffing shortages’. Many women deliver out-of-hours (three-quarters in this sample) and research will continue to examine the link between time of birth and adverse outcomes for mothers and babies.

Where did the story come from?

The study was carried out by researchers from University of Cambridge and University of Glasgow, and was funded by Medical Research Council and the Royal College of Obstetricians and Gynaecologists. The study was published in the peer-reviewed British Medical Journal.

The papers have reflected the findings of this research, but in general fail to clarify that the risk of death was small for both day and night births. It is misleading to report that the associations may be ‘due to hospital staffing shortages’, as the causes of different death rates have not been examined in this research and any such claims are based on speculation.

What kind of research was this?

This was a population-based cohort study that examined data from Scottish birth certificates and relevant databases between 1985 and 2004. It aimed to assess whether the time and day of birth had an effect upon the risk of newborn death. This particular study has the advantages of having access to a large quantity of data covering over one million births. However, it does rely on records being filled in accurately and completely.

The study did not assess the reasons behind any observed associations between time of birth and mortality risk, which could be due to a number of factors. As such, it should not be assumed that this is due to lack of skilled staff being available out of hours.

What did the research involve?

The researchers used various data sources. The Scottish Morbidity Record collects information on the outcomes for mothers and babies discharged from Scottish maternity hospitals. This record was used to identify all single-baby births between 1985 and 2004. The babies were linked to the Scottish Stillbirth and Infant Death Survey, which uses codes to record the cause of death for all babies who die around the time of birth.

The researchers were only interested in single babies born at term (between 37 and 42 weeks), with no congenital abnormalities, who were ‘cephalic’ (presenting head first) at full-term, and for whom the delivery method was recorded. They also performed a separate analysis only looking at babies who were delivered at hospital units that delivered more than 10 babies a year.

The main outcome of interest was death in the newborn, defined as death of a liveborn baby within the first four weeks of its life. The grouped births based on their day and time of delivery:

Weekday births: between 09:00 and 1700 Monday to Friday
Overnight weekday births: between 17:01 and 08:59 on weekday nights (includes Saturday morning until 08:59)
Weekend births: from 09:00 on Saturday mornings until 08:59 on Mondays
All out-of-hours births: collectively, all births at any time other than 0900-1700, Monday to Friday

The association between risk of death and time of birth was adjusted for various possible confounding factors, including characteristics of the birth, maternal characteristics and obstetric history, social and demographic characteristics, and ‘hospital throughput’ (total number of births for a given hospital in a given year).

What were the basic results?

A total of 1,039,560 live births met the specified inclusion criteria, which corresponded to over 95% of all single full-term births in Scotland for 1985-2004. Within the study cohort, 72% of births occurred out-of-hours. In total there were 539 (0.05%) newborn deaths, which was equivalent to a rate of 5.2 out of 10,000 live births. Analysis revealed that just over half of these births (273) were related to anoxia (lack of oxygen) during delivery.

During normal weekday working hours (Monday to Friday, 0900-1700) the risk of newborn death was 4.2 out of 10,000, and for all other times (out-of-hours) it was 5.6 out of 10,000: equivalent to a 30% greater incidence of death (odds ratio 1.3, 95% confidence interval 1.1 to 1.6).

They found that the increased chance of death out-of-hours was mostly related to a higher number of deaths due to anoxia (70% increased risk of death due to anoxia [a total decrease in the level of oxygen] out of hours; odds ratio 1.7, 95% CI 1.2 to 2.3). The attributable fraction of newborn deaths ascribed to anoxia during delivery out-of-hours was 26% (that is 26% of deaths related to anoxia during birth might not occur if women could deliver during normal hours rather than out-of-hours).

The associations seen were not due to confounding by maternal, infant and obstetric characteristics.

How did the researchers interpret the results?

The researchers conclude that delivery of an infant outside of the normal working week was associated with an increased risk of newborn death due to anoxia during delivery.

Conclusion

This is a well-conducted study that has analysed Scottish medical records on over one million single, full-term births to determine whether there were any association between time of birth and risk of newborn death. A particular strength of this study is the accuracy of the records used: the Scottish morbidity record reportedly has an almost 99% completion since the late 1970’s and receives regular quality assurance checks; the Stillbirth and Infant Death Survey is completed using the General Register Office, and is reportedly 100% complete.

Though there was an increased risk of newborn death out-of-hours, mostly related to deaths due to lack of oxygen during delivery, these results must be interpreted in the appropriate context:

The risk of newborn death, regardless of birth time, is very low. The rate in this large population study was 4.2 out of 10,000 during normal working hours, increasing to 5.6 per 10,000 out-of-hours. Therefore, although this relates to a 30% increased risk, the actual number of deaths for out-of-hours births is still very small.
The reasons for the observations, particularly the excess deaths due to anoxia, cannot be easily explained as the situations surrounding the adverse birth outcomes were not examined in detail.
As the researchers say, there are many possible reasons for the deaths, which may or may not be due to the variation in staffing availability at different times of the day or fewer clinical facilities available out-of-hours. However, they caution that this cannot be assumed.

Many women deliver out-of-hours (almost three-quarters of this cohort) and this is not something that can easily be controlled. A number of studies have examined the relationship between time of birth and adverse outcomes for the mother or baby, finding similar associations in some cases but no association in others. Research in this area is likely to continue, with the hope of possibly identifying any interventions that could reduce any discrepancy in outcomes between births during the normal working week, and those occurring at night or over the weekend.

Links To The Headlines

Babies born outside working hours are ‘more likely to die’. The Daily Telegraph, July 16 2010

Babies born at night three times more at risk of death. Daily Mail, July 16 2010

Out-of-hours births ‘are riskier’. BBC News, July 16 2010

100 out-of-hours babies die a year. The Sun, July 16 2010

Links To Science

Pasupathy D, Wood AM, Pell JP et al. Time of birth and risk of neonatal death at term: retrospective cohort study. BMJ 2010;341:c3498

New breast cancer drug?

Admin — Thu, 15 Jul 2010 09:40:27 +0000

British scientists are developing a new drug that could stop the spread of breast cancer in a fifth of sufferers, reported the Daily Express. It said that the drug is based on a genetic ‘breakthrough’ that identified how cells break away from highly aggressive HER2 breast cancers.

This news story was based on laboratory research looking at the role of a gene called C35 in breast cancer cells. The researchers were interested in C35 as 40-50% of breast tumours produce excess amounts of C35 protein. They found that cells producing excess amount of C35 in the laboratory take on the characteristics of cancerous cells, for example, being able to spread. The study carried out preliminary tests that found that certain chemicals could stop C35 causing some of these changes occurring in laboratory grown cells. Much more research will be needed to determine whether these chemicals might be safe and effective for testing in humans.

This research contributes to our knowledge of which genes play a role in the development of breast cancer. Such advances are important for identifying possible targets for new drug development. However, it is unfortunately much too early to say that we have a new drug for stopping the spread of breast cancer.

Where did the story come from?

The study was carried out by researchers from the University of Edinburgh and other research centres in the UK and US. It was funded by the Scottish Funding Council and Breakthrough Breast Cancer. Two of the authors work for a company called Vaccinex Inc, which discovered that C35 was a biomarker for breast cancer. The study was published in the peer-reviewed British Journal of Cancer.

The Daily Express, Daily Telegraph, and BBC News cover this story. The Express and Telegraph headlines highlight the possibility of a new drug, with the Express headline implying that the drug already exists. This claim is not supported by the current research, which solely investigated the role of a gene called C35 in breast cancer cells, but did not develop or test a ‘new drug’ to target it. The BBC News headline better reflected the findings of the research, noting that a gene involved in the spread of cancer has been found.

What kind of research was this?

This laboratory study investigated the role of a gene called C35 in breast cancer. In about a fifth of breast cancers the tumour cells have undergone a genetic mutation which results in the cell carrying multiple copies of a piece of DNA which carries the HER2 gene as well as other genes, including C35. Tumours carrying this mutation (called HER2 positive tumours) tend to be more aggressive than those that do not. This is at least in part because the cells are producing too much HER2, but could also be due to them producing more of the proteins encoded by other copied genes such as C35. The researchers wanted to investigate whether this was the case, particularly as about 40-50% of breast cancers are reported to produce excess amounts of the C35 protein.

Laboratory research is essential to furthering our knowledge of how cells become cancerous. Such knowledge can help to identify targets for new drug treatments.

What did the research involve?

The researchers used tissue samples from 122 primary breast cancers and examined whether the cells producing excess HER2 protein also produced excess C35 protein. They also took some normal breast tissue cells and genetically engineered them to produce excess C35 protein to see what happened. Finally, they looked at whether a protein called Syk which they thought might be involved was needed for C35 to have an effect. They did this by looking at whether blocking Syk with two chemicals called BAY61-3606 and piceatannol stopped C35 from having an effect on the genetically engineered cells.

What were the basic results?

The researchers found that breast cancer tissue that produced excess HER2 protein also tended to produce more C35 protein.

Normal breast tissue cells that were genetically engineered to produce excess amounts of C35 protein took on some of the characteristics of cancer cells. This included forming clumps of ‘colonies’ when grown in a soft gel in the laboratory, and spreading through such gels. The cells also lost their typical characteristics and took on the characteristics of less specialised, more immature cells; another characteristic typical of cancer cells. Further investigation showed a protein called Syk was involved in allowing C35 to have these effects. Blocking the action of Syk using the chemicals BAY61-3606 or piceatannol also blocked some of the effects of C35.

How did the researchers interpret the results?

The researchers conclude that ‘amplifying’ the C35 gene can promote a normal cell to develop the characteristics? of a cancer cell (that it, it acts as an “oncogene”) in breast cells grown in the laboratory. They suggest that drugs targeting C35 or Syk “might be helpful in treating a subset of patients with HER2-amplified breast cancers”.

Conclusion

This research contributes to our knowledge of which genes play a role in the development of cancer. Such advances are important for identifying possible targets for new drug development. Although the researchers did illustrate that chemicals known to inhibit the activity of Syk can reduce the effect of C35, much more research will be needed to determine whether these chemicals might be appropriate for use in humans.

The path to developing a new drug for use in humans is a long one and designed to be as certain as possible that the drug will be effective and safe. Therefore, even if these chemicals are successful in the laboratory, they will also have to be tested on animals before they can be tested on humans. It is much too early for newspapers to report of a new drug that stops the spread of breast cancer, but research such as this will hopefully yield new treatments in the long term.

Links To The Headlines

New drug stops deadly spread of breast cancer. Daily Express, July 14 2010

Hope of new treatment for aggressive breast cancer. The Daily Telegraph, July 14 2010

Discovery of gene in aggressive spread of cancer. BBC News, July 14 2010

Links To Science

Katz E, Dubois-Marshall S, Sims AH, et al. A gene on the HER2 amplicon, C35, is an oncogene in breast cancer whose actions are prevented by inhibition of Syk. British Journal of Cancer 2010; July 13

Birth complications for teen mums

Admin — Mon, 12 Jul 2010 21:02:24 +0000

Teenage mothers are “more likely to give birth prematurely and have underweight babies”, says The Daily Telegraph.

This news is based on research that looked at records of babies born to mothers aged between 14 and 29 in the North West of England. The study found that teenage mothers aged 14 to 17 were more likely to have preterm babies than older mothers, with the risk being greater for teenagers who had their second child before the age of 17. Teenagers’ babies were also smaller on average than the babies of older mothers, with first babies being on average 24g lighter and second babies being on average 80g lighter.

Associations between teenage pregnancy and the adverse outcomes of premature birth and lower birthweight have been observed for some time. However, even with the evidence from this study, the reasons why are unclear and theories explaining these associations remain unproven. Further research is now needed to assess whether this effect is due to the physical immaturity of teenage mothers or differences in their lifestyle and diet that affect the pregnancy.

Where did the story come from?

The study was carried out by researchers from the University of Cork and the University of Manchester, and was funded by the Health Research Board of Ireland. The study was published in the peer-reviewed medical journal BMC Pregnancy and Childbirth.

The research was covered accurately by The Daily Telegraph. The newspaper focused on the increased risk of preterm birth with a second teenage pregnancy, but did not report the risks of preterm birth associated with first teenage pregnancy. The newspaper is also likely to give the impression that this observation has been made for the first time when, in fact, several previous studies have also noticed this, and it is quite well known in the medical profession.

What kind of research was this?

This research was a cohort study designed to address whether babies born to teenage mothers were more likely to be born early or have a low birthweight. The researchers suggest that some previous studies have found that teenage pregnancy was associated with both an increased risk of preterm birth and low birthweight, although some other studies have found no association.

What did the research involve?

The researchers used a database generated from the Northwestern Perinatal Survey, undertaken at St Mary’s Hospital in Manchester between 2004 and 2006. From this database they found records of all children born to women aged between 14 and 29 years from their first or second pregnancies. The women were classified into three groups according to their age at the time of giving birth: 14-17 years, 18-19 years and 20-29 years of age.

Normal-term pregnancies are generally considered to last 37-40 weeks. In this study the researchers defined preterm delivery as greater than 33 weeks but less than 37 gestation weeks, and very preterm delivery was defined as between 23 and 33 weeks.

They assessed whether the infants had a normal birthweight or were small for gestational age (SGA) using individualised birthweight ratios. These ratios corrected birthweight for gestational age and took into account ethnic origin, gender of the baby, whether the baby was a first or second child and the height and weight of the mother. The babies were considered SGA if their individualised birthweight ratios were in the bottom 5%, and very SGA if they were in the bottom 3%.

They estimated the odds ratios (whether there was an association) between the age of the women and birth outcome of their children using a recognised statistical technique called ‘multiple logistic regression’. In their statistical analyses they adjusted for social deprivation (estimated using the mother’s postcode) and also for the mother’s ethnicity, BMI and whether it was the mother’s first or second child.

Additionally, from 2007 onwards the database contained information on whether mothers smoked at the time of their first antenatal visit. They looked at the data from births in 2007 to assess whether there was an association between smoking, young maternal age, preterm birth and birthweight.

What were the basic results?

There were records of 56,353 births. Of these:

3,636 were born to women aged between 14 and 16 years
7,506 were born to mothers between 18 and 19 years
45,211 babies were born to mothers aged between 20 and 29 years of age

The rates of teenage pregnancy were associated with increasing social deprivation, with more than one third of teenage mothers coming from the most socially deprived areas. There was an even stronger association between social deprivation score and having a second baby before 17 years of age. Teenage mothers were more likely to be underweight and to be of white ethnicity.

In first- or second-time mothers aged between 14 and 17 years the risk of preterm birth was increased relative to the older mothers (20-29 years). The risk was 21% greater during first births and 93% greater during second births (OR 1.21, 95% CI 1.01 to 1.45 and OR 1.93, 95% CI 1.38 to 2.69, respectively).

The risk of having a lower birthweight baby was also greater in mothers under 17 than in older mothers. The mean weight difference was 24g for a first child an 80g for a second child. However, the risk of having a small for gestational age baby was similar in old and young mothers once the researchers applied individualised birthweight ratios to their analyses. (In this study small for gestational age was defined as an individualised birth ratio within the bottom 5% of birthweights. Other studies consider it to be below the lowest 10% or weight below 2,500g at full-term.)

The researchers found that smoking did not seem to have an influence on preterm birth in young mothers, but say that the association between young maternal age and birthweight could be partly related to the confounding effect of smoking.

How did the researchers interpret the results?

The researchers suggest that there is an “association between second teenage delivery and preterm birth and birthweight independent of maternal social deprivation, ethnicity, BMI and smoking”. But they suggest that, unlike in previous studies, there was little evidence for an association between teenage pregnancy and risk of delivering a small for gestational age infant. They recommend that it is appropriate to encourage postnatal health education and the promotion of contraception for teenage mothers to “prevent a second teenage pregnancy with potentially higher risks of adverse outcomes”.

Conclusion

This study has provided evidence that there is an increased risk of teenage mothers having a premature baby, and that the risk further increased for teenage girls having their second child before the age of 17. However, although there are numerous theories behind these associations, this particular study did not address why this may be the case.

Some points to note:

Although the study adjusted for social deprivation, this adjustment was based on the mother’s postcode, which may not give a true representation of the mother’s living conditions and lifestyle.
The researchers also noted that there were some missing data on the potential confounding factors. However, the missing data seemed to be spread equally across the maternal age groups and so they suggest that it was unlikely to have affected their estimates.
The study only had data on maternal smoking from 2007. However, much of the analysis was conducted on data gathered between 2004 and 2006, which means it may not have been fully adjusted to account for the influence of smoking.
The researchers highlighted that maternal smoking data are often liable to miscalculation as mothers misreport their smoking status, and that many quitters are reported to resume smoking during pregnancy. It is, therefore, possible that the confounding effect of smoking in younger mothers may need further investigation. Smoking during pregnancy has been associated with both prematurity and low birthweight, so is an important confounder in a study such as this.

This study had many strengths, including the use of data from a large population and the fact that the researchers made detailed adjustments for factors influencing birthweight. Further investigation is now needed to assess whether the increased likelihood of preterm babies is due to environmental influences and the teenager’s lifestyle, or to the physical immaturity of the teenage mothers.

Overall, this study highlights the association between preterm births and maternal age, as well as the need for further research into why this is the case. This type of research might aid healthy pregnancies among younger mothers.

Links To The Headlines

Teenage mothers ‘more likely to give birth prematurely’. The Daily Telegraph, July 9 2010

Links To Science

Khashan AS, Baker PN, Kenny LC. Preterm birth and reduced birthweight in first and second teenage pregnancies: a register-based cohort study. BMC Pregnancy and Childbirth 2010, 10:36. July 9 2010

Chocolate cuts pregnancy risk claim

Admin — Mon, 12 Jul 2010 07:42:14 +0000

‘A regular chocolate treat ‘could halve a woman’s risk of giving birth prematurely,’” reported the Daily Mail.

The story is based on research that looked at whether regular chocolate consumption during pregnancy is associated with reduced risks of pre-eclampsia and high blood pressure. It found that a higher chocolate intake in the first or third trimester was associated with a lower risk of pre-eclampsia and in the first three months of pregnancy with a lower risk of high blood pressure.

This study does not provide firm evidence that chocolate consumption can reduce the risk of high blood pressure in pregnancy or pre-eclampsia. However, it does warrant further research into the possible benefits of chocolate. One important limitation is that it relied on women remembering and reporting how much chocolate they ate during pregnancy, which introduces the risk of error.

Chocolate contains caffeine, which should only be consumed in moderate amounts during pregnancy. It is also high in calories and fats. The current advice about chocolate for both pregnant women and everyone else, is to consume it as an occasional treat rather than on a regular basis. Women thought to be at risk of pre-eclampsia during pregnancy should always follow their doctors’ advice.

Where did the story come from?

The study was carried out by researchers from the University of Iowa College of Public Health and Yale University in the US. It was funded by the US National Institutes of Health. The study was published in the peer-reviewed medical journal Annals of Epidemiology.

The Daily Mail’s coverage was fair, although its headline that regular chocolate could halve the risk of premature birth was inaccurate. Premature birth can occur for many reasons, not just as a result of pre-eclampsia. At the same time, pre-eclampsia does not always lead to premature birth, although women who are at high risk may need to be delivered early.

The Mail did mention that the results may have been skewed by women being asked to remember what they had eaten during pregnancy. The newspaper also correctly pointed out that the study failed to distinguish between dark and light chocolate.

What kind of research was this?

This was part of a larger, prospective cohort study about health in pregnancy. This particular study aimed to investigate whether regular chocolate consumption during pregnancy is associated with a reduced risk of pre-eclampsia and hypertension, and whether the risks varied according to the amount of chocolate consumed. The researchers also wanted to find out if the timing or pattern of chocolate consumption during the first and third trimesters had an effect.

The researchers point out that the risk factors for pre-eclampsia are similar to the risk factors for cardiovascular disease. They say that recent studies indicate that regularly eating chocolate (in particular dark chocolate) reduces the risk of cardiovascular disease. It is thought that it does this in several ways, including lowering blood pressure, insulin resistance, blood fats and indicators of inflammation.

Many of these features also apply to pre-eclampsia, providing a ‘strong rationale’ to test for a possible protective effect of chocolate intake. To date, there have been two studies in this area, which reported conflicting results.

What did the research involve?

For their initial interview, the researchers recruited 3,591 women who were less than 16 weeks pregnant. A total of 2,967 women completed the interview, which was conducted in-person by trained personnel, usually at the women’s homes. The women were asked about their medical and reproductive history, height and weight, smoking habits, exercise habits, and alcohol and caffeine intake. They were also asked detailed questions about their chocolate consumption during pregnancy, including both drinks and foods, and asked to recall their average weekly intake of chocolate since becoming pregnant.

The women were interviewed again with the same questions directly after giving birth and asked to recall the last three months of pregnancy. The final analysis was restricted to the 2,508 women who had singleton deliveries and who had hospital delivery records available.

The researchers used the answers from both interviews to calculate consumption patterns separately for the first and third trimesters. The answers were categorised as: less than one serving of chocolate a week, one to three servings a week, and four or more servings a week. They also calculated chocolate consumption for both trimesters combined.

The researchers used blood pressure and urinary protein readings from prenatal and hospital delivery charts to categorise the women as having either high blood pressure, pre-eclampsia or normal blood pressure during pregnancy. Accepted diagnostic definitions were used to do this and the results were validated in a second sample.

The researchers used standard statistical techniques to analyse any potential association between chocolate consumption and the risk of high blood pressure and pre-eclampsia. They adjusted their figures for various potential confounders, including established risk factors for pre-eclampsia such as body mass index (BMI) and maternal age.

What were the basic results?

The researchers found that chocolate intake in the first and third trimesters of pregnancy was more frequent among women with normal blood pressure than among women who developed high blood pressure or pre-eclampsia. Of those who developed pre-eclampsia, 37.5% did not consume chocolate regularly, compared to 19.3% of women who had normal blood pressure and 24.2% of those with high blood pressure.

After adjustment, women who reported regular chocolate consumption (equal to or more than one to three servings a week) had about a 50% reduced risk of pre-eclampsia during the first trimester (OR 0.55,95% confidence interval [CI] 0.32 to 0.95) and the third trimester (OR 0.56, 95% CI 0.32 to 0.97). Only intake of chocolate during the first trimester was associated with a reduced risk of high blood pressure (OR 0.65, 95% CI 0.45 to 0.87).
Since the researchers found no difference in the size of risk between chocolate foods and drinks, they combined both sources in their analysis.

How did the researchers interpret the results?

The researchers say their findings provide ‘additional evidence’ of the benefits of chocolate and that further studies are needed to confirm and explain the protective effects of chocolate intake on the risk of pre-eclampsia.

They say that the current understanding of pre-eclampsia as a ‘2-stage disease process’ makes it biologically plausible that trimesters one and two would be ‘critical windows’ for possibly lowering the risk.

Conclusion

The findings from this well-conducted study warrant further research, but do not provide firm evidence that chocolate can protect against pre-eclampsia. One problem is the possibility of ‘reverse causality’, with women who developed high blood pressure in pregnancy possibly being less likely to consume chocolate after diagnosis. Although the researchers say that they took account of this possibility by excluding women with high blood pressure before 20 weeks gestation, it is not certain that this applies to the later analyses. They also claim that the protective effects of chocolate were apparent in the first trimester.

A strength of the study is its size, with a large cohort of women being asked detailed questions about chocolate consumption both in early pregnancy and just after delivery. Classification of pre-eclampsia and high blood pressure were also based on accepted definitions and the researchers controlled for risk factors that might influence the outcomes they were studying.

As the authors note, the study has several limitations:

The women self-reported their chocolate consumption and had to recall their consumption over a relatively long period of time, which raises the chance that errors were introduced.
It did not differentiate between dark and other types of chocolate.
No direct measures of any biomarkers were taken (such as theobromine) to validate associations between self-reported chocolate consumption and the risk of pre-eclampsia and high blood pressure.
It did not assess what else the women were eating during pregnancy, other than caffeine, which could have skewed the results, although the researchers point out that diet is not currently thought of as a risk factor for pre-eclampsia.
The findings could be biased by underreporting of chocolate intake by overweight women although the researchers say re-ran their analyses to take account of this and got the same results.
Although many confounders were taken into account, the results could still have been affected by some of these or other unmeasured confounders, such as other foods or drinks associated with chocolate eating that were not recorded.

Women thought to be at risk of pre-eclampsia during pregnancy should always follow their doctors’ advice.

Links To The Headlines

A regular chocolate treat ‘could halve a woman’s risk of giving birth prematurely’. Daily Mail, July 9 2010

Links To Science

Saftlas AF, Triche EW, Beydoun H, et al. Does Chocolate Intake During Pregnancy Reduce the Risks of Preeclampsia and Gestational Hypertension? Annals of Epidemiology 2010; 20: 584-591

Measles outbreak in France – Holiday Parents Warned

Admin — Sun, 11 Jul 2010 14:13:57 +0000

French authorities have reported an increased number of measles cases in France this year.

Parents who are planning a holiday in France and have not had their children vaccinated against measles should ensure their children have the measles, mumps and rubella (MMR) vaccine.

It is never too late to get the MMR vaccine for your child as it provides the best possible protection against measles, mumps and rubella.

Your GP can provide advice on vaccination or you can visit the vaccination pages on NHS Choices for more information.

At what age can you have MMR?

The MMR vaccination can be given from around one year of age.

Is it necessary to have both doses to be protected?

Studies show that a single dose of a vaccine containing measles, such as MMR, protects against the disease in about 90% of people. Two doses are recommended for the best protection.

Can adults have MMR if they didn’t have it when they were younger?

Yes. Travellers to areas where measles is common should ensure that they are fully immunised.

I’m going on holiday soon and there isn’t time to give my child the MMR vaccine. What should I do?

If there isn’t time to get the MMR vaccination before you go away, book an appointment with your GP for your child to have it as soon as you get back.

While you are away, initial symptoms of measles to look out for are:

a rash for at least three days, and
fever for at least one day, and
at least one of the following: a cough, a head cold or red sore eyes

What should I do if I’m abroad and I think my child has measles?

Seek medical advice immediately. Make sure you have an up-to-date European Health Insurance Card (EHIC) before leaving the UK. The EHIC is not a substitute for medical and travel insurance (you should have this as well), but it does allow you to have emergency medical treatment on the same terms as French nationals.

More information about measles

NHS Choices information about measles

NHS Choices information about MMR

Travel advice on getting treatment abroad is on the Foreign and Commonwealth Office’s website

Fish oil ‘may fight breast cancer’

Admin — Thu, 08 Jul 2010 18:08:08 +0000

Fish oil may cut the risk of breast cancer by a third, says the Daily Mail.

The news is based on a large study that followed just over 35,000 postmenopausal women for up to seven years to investigate how their use of supplements, including fish oil, affected their risk of developing breast cancer. It found that women currently using fish oil supplements had a reduced risk of developing ductal carcinoma, the most common type of breast cancer.

While the size of this study was a strength, it has several important limitations such as not measuring the dosage or frequency of fish oil. Also, the small size of some groups in the study, and the use of multiple statistical analyses, that increase the likelihood that associations have been found by chance.

This large study warrants further research into possible association between fish oil supplements and the risk of breast cancer, but until these results are confirmed by further studies, it is too early to recommend fish oil supplements as a method of breast cancer prevention, as the researchers of this study themselves conclude.

Where did the story come from?

The study was carried out by researchers from the University of Washington and the University of California in the US. It was funded by the US National Cancer Institute and published in the peer-reviewed medical journal, Cancer Epidemiology, Biomarkers and Prevention.

The Daily Mail’s report of the study was accurate and did mention the study authors’ conclusions that further research is needed. It also featured a quote from an independent expert who implied that the results of a single study are not normally sufficient evidence to make any health recommendations. It did not mention the important limitations of this research.

What kind of research was this?

This was a prospective cohort study that aimed to investigate the possible association between the use of ‘speciality supplements’ and breast cancer risk. The authors define speciality supplements as non-vitamin, non-mineral supplements promoted used for various purposes, such as glucosamine, black cohosh (often taken for menopausal symptoms), St John’s wort, garlic pills, acidophilus, Coenzyme Q10 and fish oils.

They point out that use of these supplements has increased substantially over recent decades and that several have been claimed to have anti-inflammatory or anticancer properties. Despite their rise in popularity, there have been no prospective studies looking at their long-term use and breast cancer risk, the researchers say.

Cohort studies, in which large groups of people are followed for many years, are useful in helping to assess potential links between lifestyle factors (in this case, taking supplements) and health outcomes. However, a randomised controlled trial could more reliably demonstrate whether taking a particular supplement affected the risk of breast cancer over time.

To make it possible to detect small differences in the rates breast cancer developed, any randomised controlled trial performed would need to recruit a large number of women and follow them for a sufficient period of time, which may not be practical.

What did the research involve?

Between 2000 and 2002, the researchers recruited 40,337 postmenopausal women, aged between 50 and 76 years. These women were members of a larger cohort designed to specifically look at possible links between all types of supplements and cancer risk.

At entry into the study the women were asked to complete a 24-page questionnaire that included a detailed assessment of supplement use, both currently and during the 10 years prior to the study start. They were asked how often they took supplements and for how many years. Information was also gathered from the women on known and suspected risk factors for breast cancer including BMI, physical activity, medication use, family and medical history and diet. The researchers excluded any women reporting breast cancer or a history of cancer, leaving a total of 35,016 for inclusion in the study.

The women were then followed from 2000 to 2007, to see who developed breast cancer. This was determined using these results from a cancer registry. The researchers then used established statistical methods to analyse any association between supplement use and breast cancer risk. Their models were adjusted to take account of many other things that might influence risk, such as known risk factors, age, race, reproductive history, alcohol consumption, use of hormone replacement therapy and diet.

What were the basic results?

The researchers found that women who reported they were currently using fish oil had a 32% reduced risk of ductal breast cancer, the most common type (hazard ratio [HR)], 0.68; 95%, confidence interval [CI], 0.50-0.92), but not of a type called lobular cancer.

There was no significant reduction in risk for women who had used fish oil supplements in the past. However, more frequent use over the past 10 years demonstrated a non-significant trend towards decreasing risk of breast cancer:

low use was associated with a non-significant 25% reduction in risk when compared to non-use
high use was associated with a non-significant 18% reduction compared to non-use

None of the other supplements, including those often used for menopausal symptoms, such as black cohosh and dong quai, were associated with either higher or lower risk of breast cancer.

How did the researchers interpret the results?

The researchers say that fish oil may reduce the risk of ductal but not lobular breast cancer and that this warrants further investigation. This should focus on the timing of exposure and the dose, as well as the mechanism of action that might explain the different effects by cancer stage or type. They stress that until these results are confirmed by further studies, fish oil supplements should not be promoted for preventing breast cancer.

Conclusion

This large study is likely to be one of the first to assess any association between specialty supplements and breast cancer risk. It has strengths in that it carried out a detailed assessment of supplement use in 35,016 women, and also adjusted for numerous known and suspected risk factors for breast cancer (possible confounders) when calculating cancer risk by supplement use.

However, the study provides no firm evidence that fish oil supplements reduce breast cancer risk and therefore they should not be recommended for this purpose. Further research is needed.

It is important to note that:

The study carried out multiple statistical analyses examining the relationships between breast cancer and the use of numerous supplements, in addition to other medical and lifestyle factors. The multiple analyses increase the possibility of finding associations by chance.
Of all the supplements examined, a link was only found with current use of fish oil supplements (at study start); however, only 47 women who were currently taking cod liver oil at study start went on to develop breast cancer meaning this small number again increases the risk of chance findings on statistical analysis.
The questionnaire asked about ‘current use’ of fish oil a term that provides little information on the preparation, dose, frequency or duration of use. However further analysis of pattern of use over 10 years demonstrated no significant effect on breast cancer risk.
Although researchers tried to exclude women with a cancer history and certain risk factors for breast cancer at the start of the study, it is possible that some of the women in the study had undiagnosed breast cancer at the time, which could have affected results.
The study only followed up women until 2007, with an average follow-up of six years. This is a relatively short period and many cases of breast cancer may go on to develop after this time. Diagnoses of breast cancer after the follow-up date could have affected the results.
Although it tried to control for potential confounders, there is always a possibility that in this type of study, both measured and unmeasured confounders could be having an effect.
The study relied on the women self-reporting their use of supplements and the factors that might have affected their risk of breast cancer. This may have introduced some inaccuracy.
The study was specifically of postmenopausal women, and results may be different if supplement use were studied in premenopausal women.

Links To The Headlines

Fish oil may cut breast cancer risk ‘by a third’. Daily Mail, July 8 2010

Fish supplements may reduce risk of cancer. The Independent, July 8 2010

Fish oil cuts cancer risks. Daily Mirror, July 8 2010

Links To Science

Brasky TM, Lampe JW, Potter JD et al. Specialty Supplements and Breast Cancer Risk in the VITamins And Lifestyle (VITAL) Cohort. July 2010 19; 1696

Test ‘may predict menopause’

Admin — Thu, 08 Jul 2010 07:35:57 +0000

A blood test to predict when menopause will occur “could close the baby gap” by telling women how long they will remain fertile, reported The Guardian. Several other newspapers have reported on the hormone-based menopause test, saying that home testing kits could be available in a few years.

The news story is based on a study that has been presented at fertility conference but has not yet been published, meaning it is difficult to assess the methods and quality of this research. However, the limited information available suggested the study was small and relatively short, and further testing will be needed.

It is important to stress that a woman’s fertility level and ability to conceive start to decline long before her periods stop and, therefore, a test predicting menopause may be of limited value in this area. Also, fertility levels can be affected by other factors, such as the quality of a man’s sperm or blocked ovarian tubes in the woman. The test may have a role in predicting early menopause, although further results are needed to confirm this.

Where did the story come from?

News reports about this test are based on a press release and conference abstract presented at the 2010 conference of the European Society of Human Reproduction and Embryology.

These documents present only limited details of a study carried out by researchers from Shaheed Beheshti University of Medical Sciences in Iran. No information is available as to if or when the research may be published in a peer-reviewed journal, or about how the research was funded.

The results presented in the press release were reported accurately, if uncritically, by most newspapers. Most papers also published comments from independent experts, who set the research in context and addressed the fact that such a test is only of limited use to most women because fertility levels start to fall well before the menopause occurs. The Daily Mail said that a home testing kit could be on sale within three years, but it is unclear on what this prediction is based.

None of the reports pointed out that their information was based on a conference abstract and press release and that the full results have not yet been published.

What kind of research was this?

This particular piece of research aimed to test a statistical model developed to accurately predict the age at which the menopause would occur. The model is based on assessing levels of a hormone called anti-mullerian hormone (AMH), which is produced by the ovaries. AMH controls the development of ovarian follicles from which eggs develop, and some experts have suggested it could be a marker for ovarian function. The researchers wanted to test whether measuring AMH at various ages could predict when women would reach the menopause.

What did the research involve?

There is only limited information available on the methods used in this research. However according to the abstract and press release, the researchers took blood samples to measure blood levels of AMH in 266 women, aged 20-49, randomly selected from a larger, prospective cohort study called the Tehran Lipid and Glucose Study. This ongoing study aims to identify cardiovascular risk factors among the Iranian population.

In this smaller study, the researchers measured AMH levels twice more, at three-yearly intervals. They also collected information on the women’s reproductive background and reproductive history. They then developed and tested a statistical model for estimating the women’s age at menopause using a single measurement of AMH in blood samples.

What were the basic results?

Information on the results is also limited but the researchers say they found a “high degree of correlation” between the estimated ages at menopause provided by their formula model and the actual age at menopause seen in a subgroup of 63 women who reached menopause during the study. The average difference between the predicted age using the model and the women’s actual age was only a third of a year and the maximum margin of error of three to four years.

Using this statistical model, the researchers say they were able to identify the specific AMH levels at different ages (20, 25 and 30 years) that would predict if women were likely to have an early menopause (before 45) or reach menopause over 50 years. Among the group studied, the average age at the menopause was 52 years.

How did the researchers interpret the results?

The researchers say their study suggests that the AMH can be used to precisely forecast the age at menopause, even in young women. Larger studies that follow women in their 20s for several years are needed to validate the accuracy of the measurements, they add.

Conclusion

This was a small study carried out over a limited period (about six years), which tested whether levels of AMH in women of reproductive age could be used to predict the age they will reach the menopause. It seems to have been designed with a reasonable cut-off point set for the test, the first step in preparing a potential test for clinical use. Since the study has not been published yet, it is not possible to give detailed information about its methods or results. However, if validated by further studies, such a test could be particularly useful in predicting early menopause, giving women who may experience it time to plan their future.

The fact that so far only 63 women actually reached menopause in the study and only three of them were under 45, means the mathematical formula has only undergone limited testing. It should be stressed that until there are larger studies following women from the age of 20 to the age they actually reach menopause, the method the researchers used has not been proven.

As with all studies assessing a diagnostic test, it will be important to follow up this initial study with others, setting a cut-off point that can establish the sensitivity and specificity of the test. What is needed are statistical measures that relate to the number of women correctly identified by the test as going on to an early menopause (or late menopause) and also the number of women incorrectly identified or predicted as heading for early or late menopause when they do not. These results, when published, will help decide the true value of the test.

Links To The Headlines

Menopause test to tell you when it’s too late for a baby. Daily Mail, June 28 2010

Blood test to predict menopause on horizon. Daily Mail, June 28 2010

Menopause test hope. Daily Mirror, June 28 2010

Menopause test could close the baby gap. The Guardian, June 28 2010

Menopause ‘prediction’ test hope. BBC News, June 28 2010

Links To Science

European Society of Human Reproduction and Embryology

European Society of Human Reproduction and Embryology: 2010 Annual Meeting

Mobiles not linked to child cancer

Admin — Tue, 06 Jul 2010 11:02:54 +0000

A new study has found no link between exposure to mobile phone masts while in the womb and the risk of developing early childhood cancers, newspapers have reported.

During the study, scientists used complex transmitter data to estimate the signal exposure levels that almost 1,400 children with childhood cancers had experienced before birth, comparing them to the exposure levels of approximately 5,600 children not affected by cancer. The researchers specifically looked at three different measures of exposure – distance to nearest base station, total power output from nearby base stations, and estimated power density from nearby base stations. None of these measures suggested any association with the likelihood of cancer.

The rarity of childhood cancers and the practical constraints of individually measuring women’s exposure mean that the study authors had to make various assumptions about exposure, which may have affected the results seen. However, the study seems robustly planned and executed overall. Another limitation is that the study only looked at exposure during pregnancy and early childhood cancers, meaning it cannot tell us about exposure during childhood, or about longer-term outcomes.

Where did the story come from?

The study was carried out by researchers from the School of Public Health at Imperial College London, and funded by the UK Mobile Telecommunications Health Research (MTHR) Programme, an independent body set up to fund research into the possible health effects of mobile telecommunications. The MTHR is jointly funded by the UK Department of Health and the mobile telecommunications industry. The study was published in the peer-reviewed British Medical Journal.
This research was well reported by The Guardian and The Independent.

What kind of research was this?

This was a case-control study looking at whether there was a relationship between mothers’ exposure to mobile phone masts in pregnancy and early childhood cancers in their offspring.
This study design takes a group of individuals with the condition of interest (a case group of children with early childhood cancers) and compares their past exposures with a group of individuals who do not have the condition of interest (a control group). This study design is often used when the condition of interest is rare – as is the case with early childhood cancers – as a cohort study would have to be very large to detect enough individuals with the condition to allow a meaningful analysis.

One of the limitations to this study design is that the exposures being assessed occurred in the past, and therefore it can be difficult to assess them accurately, particularly if researchers rely only on people’s recall of events. However, in this study, researchers did not have to rely on people remembering or estimating their exposure to mobile phone masts, instead they used data on where individuals lived and known locations of mobile phone masts. This increases the reliability of the information about exposure.

What did the research involve?

The researchers analysed data from 1,397 children aged up to four years old who had cancer (the case group). They were compared with 5,588 children without cancer (the control group) who were matched to the cases for gender and date of birth. They determined where the children’s mothers had lived during their pregnancy, and how near that was to a mobile phone mast. They then compared the cases and controls to see if their mothers had lived at different distances from mobile phone masts, or whether they were exposed to different levels of power output from these masts.

To gather a suitable case group the researchers had identified all children in Great Britain aged up to four years old who were registered as having cancer in the national cancer registries for 1999 to 2001. They also noted which types of cancers these children had. For the 1,926 cases of early childhood cancer identified, there was sufficient data to include 1,397 of the children in the analyses (73%). For each child with cancer, they used national birth registries for Great Britain to identify four matched controls: children of the same sex born on the same date, and who were not recorded as having cancer in the national cancer registries.
For each child the researchers used their registered address or postcode at time of birth. They excluded children without a valid birth address or postcode. The four national mobile phone operators at the time of the study (Vodafone, O2, Orange and T-Mobile) provided information on all 81,781 mobile phone antennae in use from January 1 1996 to December 31 2001. This included where the antennae were, how many there were at each site (base station), dates at which they started and ended transmission, and features including the type of antennae, orientation, height above ground level, beam width, power output and frequency.
The researchers excluded 4,891 low-power antennae covering limited areas (called microcells, and accounting for 6% of the antennae). In total the researchers had full data on 66,790 (87%) of the 76,890 remaining antennae. Where data was missing, it was estimated using the data that the researchers had on other antennae, or was assigned the average (median) value for the company.
For each child, the researchers calculated the distance from the nearest base station, the total power output from all base stations within 700m (at ground level power density is reported to drop off rapidly after 500m). They also calculated ‘power density’ for base stations within 1,400m, essentially how much power was concentrated in a given area (exposures from over 1,400m away were considered to be at background levels).

The researchers had based their calculations of power density in a given area on measurements taken in a survey of a rural area (151 sites around four base stations) and an urban area (50 sites). These calculations used complex mathematical models, which were checked against data obtained from other surveys and measurements. The model appeared to perform better in predicting power density in rural areas than in urban areas. Pregnancies were assumed to last nine months, and exposure over the nine months prior to birth was estimated for each child.

The researchers looked at how mobile phone mast exposure in the womb related to an outcome of any childhood cancer and to specific cancers (brain and central nervous system cancers, leukaemia, and non-Hodgkin’s lymphomas). They took into account factors that could affect results, including socioeconomic deprivation, population density and population mixing (migration into the area in the previous year). Data on these factors was obtained from the 2001 census for the small area containing the birth address (census output area).

What were the basic results?

Of the 1,397 cancer cases, 527 were leukaemia or non-Hodgkin’s lymphoma (38%), and 251 were cancers of the brain or central nervous system (18%). Cases and controls were similar in terms of social and demographic characteristics.
The researchers also found that:
• Children who had cancer had birth addresses 1,107m from the nearest base station on average.
• Controls had birth addresses 1,073m from the nearest base station on average.
• There was no significant difference between children with early childhood cancer and controls in distance of birth address from the nearest base station.
• There was no significant difference between the children with cancer and the controls in terms of total power output or modelled power density exposure at their birth addresses while in the womb.
Distance from nearest base station, total power output and modelled power density did not differ between healthy controls and children with specific cancer types (either leukaemia and non-Hodgkin’s lymphoma, or brain and central nervous system cancer).

How did the researchers interpret the results?

The researchers concluded that they found “no association between risk of childhood cancers and mobile phone base station exposures during pregnancy”. They say that their results “should help to place any future reports of cancer clusters near mobile phone base stations in a wider public health context”.

Conclusion

This study appears well conducted. Its strengths include:
• Analysis of data from children born across Great Britain and inclusion of a high proportion (73%) of all registered early childhood cancer cases in Great Britain for the period assessed (1999-2001). This reduces the possibility that the area or children selected may not be representative of most cases.
• The use of three different measures to assess exposure to mobile phone base stations during pregnancy, none of which showed an association between exposure and childhood cancer.

The study’s limitations include:

• Only assessing the effects of exposure during pregnancy on early childhood cancers (up to age four). Longer-term effects or effects of later exposure during infancy and childhood were not assessed.
• Researchers did not measure individual exposure and therefore had to use surrogate measures of exposure – these may not fully capture or reflect individual exposure. Although measuring individual exposure would have been more accurate, doing so with a large cohort of pregnant women would be unlikely to be feasible.
• The researchers had to make certain assumptions in order to carry out their analyses. For example, they assumed that all pregnancies lasted nine months and calculated exposures based on registered birth address. In some cases, pregnancies may have been shorter or slightly longer than nine months, and mothers may have moved house or have spent significant amounts of time in other areas (eg for work). The accuracy of the assumptions may affect the results.
• The researchers were not able to assess radiofrequency exposure from other sources, such as low power mobile phone antennae, maternal use of mobile phones in pregnancy, radio or TV transmitters, or cordless phone base stations.
• The technology used in mobile phone masts may have changed since the study assessment period (1996-2001), therefore results may not be representative of modern exposure levels
• Although the researchers took into account factors that could affect results, these or other factors may still be having an effect.

Links To The Headlines

No link to child cancer from phone masts, finds study. The Guardian, June 23 2010
Study finds no link between phone masts and childhood cancers. The Independent, June 23 2010
Links To Science
Elliott P, Toledano MB, Bennett J et al. Mobile phone base stations and early childhood cancers: case-control study. British Medical Journal, 2010;340:c3077
Editorial: Bithell JF Childhood cancer and proximity to mobile phone masts. British Medical Journal, 2010;340:c3015