New Study Suggests Link Between BMI During Pregnancy and Birth Defect Risk

Being overweight or obese when you're pregnant could be linked to a risk of birth defects for your baby.

overweight on pregnancy hin255/Shutterstock
Being overweight or obese before and during pregnancy has already been linked to potential complications for the mom-to-be, but a new study published in BMJ links a high BMI with a woman's increased risk of having children with birth defects.

This was a large study: Researchers looked at over a million women to observe the link between weight and the risk of giving birth to babies with congenital malformations. According to their findings, 3.4 percent of women who were underweight or within the healthy weight range gave birth to babies with these malformations. About 3.5 percent of the women in the overweight group gave birth to babies with congenital defects. Researchers divided women in the obese range into the three categories based on body mass index: Those in the obesity class 1 group (who had BMIs between 30 and 45) had a 3.8 percent rate of babies with congenital defects, which rose to 4.2 percent among moms in the second obesity class (who had BMIs between 35 and 40). Mothers in the obesity class 3 group had BMI ratings of over 40, and their offspring had a 4.7 rate of this issue. 

The difference among these rates may not seem like much, but every mother wants to do do everything in her power to protect her children against negative outcomes. The reassuring part of these findings? Even if moms are unable to get to the healthy weight range, they can presumably bring down their risk by lowering their BMI scores even just incrementally, as results indicate that women on the higher end of the obese range have greater risk than those on the lower end.

This news further highlights this importance of adopting a healthy lifestyle before you even get pregnant. Obviously, it can be tough to hear that your weight could affect your baby's health—but it's not about a number on a scale, it's about the health implications that come with it. Researchers believe this study indicates that maintaining a healthy weight during pregnancy often makes for the best maternal and fetal outcomes.

Does this mean that overweight women will always give birth to babies with birth defects? Absolutely not. It does, however, point to a relationship that's important to consider. BMI doesn't always tell the whole story, so if you fall in the overweight or obese range, we suggest having a conversation with your doctor and, if he or she believes you may be at risk, doing whatever you can to maintain the healthiest lifestyle possible, for you and your baby.