Women who are obese when they become pregnant have a higher than normal risk of delivering babies with birth defects, such as spina bifida and cleft palates, finds a new study.
The report, published in this week's Journal of the American Medical Association, is a review of previously published work. The research team, led by Katherine Stothard at Newcastle University in Great Britain, pooled the results of 18 studies, and reviewed the findings of 39 other studies. They found a clear link between a mother's obesity and her child's risk of a birth defect.
Among the most significant findings:
- The risk of spina bifida was more than twice as high for obese pregnant women.
- The overall risk of neural tube defects was nearly twice as high.
- The risk of cardiovascular defects was 30 per cent higher.
- The risk of cleft lip and cleft palate, either singly or together, was about 20 per cent higher.
- The risk of hydrocephaly (an abnormal buildup of fluid in the brain) was 60 per cent higher.
- Limb reduction abnormalities were 30 per cent higher.
The definitions of overweight and obese differed somewhat from study to study, but many studies used those set by the World Health Organization -- a body mass index or BMI of 25 and above for overweight and 30 and above for obese.
Exactly how obesity increases birth defect risk isn't known, but the researchers offered possible explanations. It could be that the women become deficient in certain nutrients, particularly folate, because of poor eating habits. Or they may have had undetected diseases such as diabetes.
Finally, because ultrasound monitoring of obese patients is more difficult, it could have meant that there were more missed cases of deformities like neural-tube defects.
The study highlights the need for both doctors and patients to be aware of the added risk that a mother's obesity places on the developing baby. Doctors should not only advise women who are planning to become pregnant to maintain a healthy weight, but also ensure that those who are already pregnant receive proper nutrition
The authors say they would now like to look at whether a mother simply being overweight is linked to an increased risk of birth defects.
