Page last updated at 01:29 GMT, Wednesday, 11 February 2009
Obese mothers 'risk spina bifida'
pregnant woman exercising
Women should remain active during pregnancy
Mothers-to-be who are obese increase their odds of having a baby with abnormalities including spina bifida, researchers say.
Their analysis of data from 39 studies found obese women were more than twice as likely to have a baby with spina bifida or another neural tube defect.
The risk of heart defects and cleft lip was also raised, the Journal of the American Medical Association says.
Up to a fifth of pregnant mothers in the UK are classed as obese.
Leading clinicians said the government should be focussing anti-obesity campaigns on women of child-bearing age.
Women who are thinking about trying for a baby need to check their own weight first and then think about seeking help if they are overweight
Lead researcher Dr Judith Rankin
It is well known that women who are obese are more likely to have difficulty conceiving and once they are pregnant, overweight and obese women and their babies are at a greater risk of a range of health problems.
However, this is the first time that so many studies have been combined to build a more accurate picture of the risks to the unborn child, according to lead researcher Dr Judith Rankin of Newcastle University.
"Given that we are seeing an increase in the number of people who are overweight or obese, then we may see an increase in the number of babies born with abnormalities," she said.
However, she stressed these abnormalities were uncommon.
"Spina bifida only occurs in approximately one in every 2,000 births, so the risk, even among obese women, remains very low.
"Women who are thinking about trying for a baby need to check their own weight first and then think about seeking help if they are overweight.
"While you are pregnant it's not the time to start a weight loss diet but it is more important to eat sensibly and healthily," she said.
The Royal College of Midwives echoed this advice.
Dr Rankin's team will now continue the work to examine why there is a link between a mother's weight and abnormalities in the baby. They say it could be related to nutritional deficiencies or undetected diabetes in the mother.
Both maternal diabetes and a lack of folic acid are established risk factors for birth abnormalities, particularly neural tube defects which affect the brain and spinal cord.
Andrew Russell, chief executive of the Association for Spinal Bifida and Hydrocephalus, said: "Folic acid does seem to be involved. It is very important for women planning a pregnancy or likely to fall pregnant to take a folic acid supplement."
BODY MASS INDEX
Calculated by dividing weight in kilograms by height in metres squared
Normal: 18.5 - 24.9
Overweight: 25 - 29.9
Obese: Above 30
Calculate your BMI
Experts from the Royal Society of Medicine believe the government should be funding campaigns to target women of child-bearing age.
The RSM's president of the Obstetrics & Gynaecology section, Professor Philip Steer, said: "We've had warnings on cigarette packets telling us that smoking can harm the unborn baby as well as the mother. But there seems to be little effort made to warn mothers about the risk obesity poses to mother and child."
A Department of Health spokeswoman said: "Our advice is that all women should aim to embark on pregnancy as fit and as healthy as possible. To this end, we have introduced a range of initiatives to help people stop smoking, including free NHS services, and eat healthy."
By 2015, it is expected there will be 2.3 billion overweight and more than 700 million obese adults worldwide.
Obese is considered as a Body Mass Index (BMI) over 30, while overweight is classed as a BMI over 25. BMI is calculated by dividing your weight in kilograms by your height in metres squared.
Maternal Overweight and Obesity and the Risk of Congenital Anomalies
A Systematic Review and Meta-analysis
Katherine J. Stothard, PhD; Peter W. G. Tennant, MSc; Ruth Bell, MD; Judith Rankin, PhD
Context Evidence suggests an association between maternal obesity and some congenital anomalies.
Objective To assess current evidence of the association between maternal overweight, maternal obesity, and congenital anomaly.
Data Sources MEDLINE, EMBASE, CINAHL, and Scopus (January 1966 through May 2008) were searched for English-language studies using a list of keywords. Reference lists from relevant review articles were also searched.
Study Selection Observational studies with an estimate of prepregnancy or early pregnancy weight or body mass index (BMI) and data on congenital anomalies were considered. Of 1944 potential articles, 39 were included in the systematic review and 18 in the meta-analysis.
Data Extraction and Synthesis Information was extracted on study design, quality, participants, congenital anomaly groups and subtypes, and risk estimates. Pooled odds ratios (ORs) comparing risk among overweight, obese, and recommended-weight mothers (defined by BMI) were determined for congenital anomaly groups and subtypes for which at least 150 cases had been reported in the literature.
Results Pooled ORs for overweight and obesity were calculated for 16 and 15 anomaly groups or subtypes, respectively. Compared with mothers of recommended BMI, obese mothers were at increased odds of pregnancies affected by neural tube defects (OR, 1.87; 95% confidence interval [CI], 1.62-2.15), spina bifida (OR, 2.24; 95% CI, 1.86-2.69), cardiovascular anomalies (OR, 1.30; 95% CI, 1.12-1.51), septal anomalies (OR, 1.20; 95% CI, 1.09-1.31), cleft palate (OR, 1.23; 95% CI, 1.03-1.47), cleft lip and palate (OR, 1.20; 95% CI, 1.03-1.40), anorectal atresia (OR, 1.48; 95% CI, 1.12-1.97), hydrocephaly (OR, 1.68; 95% CI, 1.19-2.36), and limb reduction anomalies (OR, 1.34; 95% CI, 1.03-1.73). The risk of gastroschisis among obese mothers was significantly reduced (OR, 0.17; 95% CI, 0.10-0.30).
Conclusions Maternal obesity is associated with an increased risk of a range of structural anomalies, although the absolute increase is likely to be small. Further studies are needed to confirm whether maternal overweight is also implicated.
Author Affiliations: Institute of Health and Society, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
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