Obesity During Pregnancy is Dangerous for Baby

Obese women are more likely to have babies with rare but serious birth defects, including spina bifida and other neural tube defects, and to a lesser degree heart anomalies, cleft palate and hydrocephaly, a new study confirms.

The latest research, which pooled and analyzed dozens of earlier studies, found that the risk of spina bifida was 2.2 times higher for babies of obese mothers compared to infants of normal weight women, while the risk of other neural tube defects was 1.8 times higher. The babies of obese mothers faced smaller increases in risk for heart defects, stunted limbs, a congenital malformation of the anal opening, and hydrocephaly, also called water on the brain.

The paper appeared on Wednesday in the Journal of the American Medical Association.

“Our findings confirm what studies have been finding with regard to neural tube defects, particularly spina bifida, and some heart anomalies,” Judith Rankin, senior author of the study and a researcher at the Institute of Health and Society at Newcastle University in the United Kingdom, said in an e-mail message. “However, we were surprised at the range of birth defects that were found to have an increased risk in mothers who were obese.”

The researchers analyzed the results of 39 previously published articles and pooled the results in order to compare risks among babies born to women who were at the recommended weight, overweight or obese.

They noted a slightly higher risk for neural tube defects and heart anomalies among babies born to women who were merely overweight but not obese, but said more research should be done to confirm these findings.

Dr. Laura Riley, medical director of labor and delivery at Massachusetts General Hospital in Boston, said she was skeptical of the findings regarding babies of overweight women. She pointed out that pre-pregnancy weight is often self-reported in studies, adding, “People lie about their weight.”

If obese women underestimated their pre-pregnancy weight in their reports, they may have inadvertently been included in the category of overweight rather than obese mothers, skewing the results, she said.

Women who are planning a pregnancy are advised to take folic acid supplements even before conception, in order to reduce the risk of potentially serious neural tube defects, including spina bifida. But Dr. Rankin suggested that insulin resistance and undiagnosed diabetes, rather than insufficient folic acid, may be playing a causative role in birth defects among babies born to obese women, though the precise mechanism is not known.

“This confirms what we know and certainly tells us the association between obesity and neural tube defects is real,” said Dr. Riley, adding that she routinely advises her obese patients to lose weight or consider bariatric surgery before becoming pregnant.

The desire to have a healthy baby can be very motivating, she noted. “The mother’s instinct is to be very concerned about her baby,” she said. Telling women who want to have children about the risks related to obesity “really perks people up," she added. "They stop and think about it.”