A new study showed that obese women were more likely to deliver babies with rare but serious birth defects, such as spina bifida and other neural tube defects, and to a lesser degree heart anomalies, cleft palate and hydrocephaly.

This latest study pooled and analyzed dozens of earlier studies and found that the risk of spina bifida was 2.2 times higher for babies of obese mothers 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.

A slightly higher risk for neural tube defects and heart anomalies among babies born to women who were merely overweight but not obese.

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. However, researchers believe 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. The precise mechanism is, however, not known.

Doctors should advise their obese patients to lose weight or consider bariatric surgery before becoming pregnant. The researchers say that desire to have a healthy baby should be very motivating as mother’s instinct is to be very concerned about her baby. Telling women who want to have children about the risks related to obesity “really perks people up”.

If women were so worried about their baby’s health, wouldn’t they stop smoking immediately after realizing they were pregnant? Instead, few actually give up smoking in pregnancy although smoking is associated with premature births, low birth weights, still births and SIDS.