HOUSTON (February 24, 2009)

To the long list of risks associated with obesity, add a wider than expected range of birth defects that are more likely to occur in babies born to obese women.

A new analysis in the Journal of the American Medical Association found that women who were obese (defined as having a BMI of 29 or greater) before pregnancy were:

  • more than twice as likely to have a baby born with spina bifida
  • nearly twice as likely to have a baby with other neural tube defects
  • more likely to have a baby with heart problems, cleft palate or cleft lip, abnormal rectum or anus development, and hydrocephaly (excess fluid build-up in the brain)

The researchers offered three theories that might explain their findings:

  1. many obese women might also have undiagnosed diabetes, which can lead to abnormal development of a fetus
  2. obese moms-to-be might be eating a diet that is not as nutritionally sound as that of normal weight women
  3. obese women are more likely to be missing nutrients like folic acid that are vital to preventing birth defects such as neural tube defects

They also noted a slightly higher risk for neural tube defects and heart problems in babies born to women who were overweight but not obese, but said further studies are needed to confirm a link.

What This Means to You

One of the most important things women who are planning to start a family can do to help prevent serious birth defects is to get enough folic acid every day - especially before conception and during early pregnancy. Studies have shown that women who get 400 micrograms (0.4 milligrams) daily prior to conception and during early pregnancy reduce the risk that their baby will be born with a serious neural tube defect (a birth defect involving incomplete development of the brain and spinal cord) by up to 70%.

Women trying to conceive also should try to maintain their recommended weight and ask their doctors if they should be tested for undiagnosed diabetes. And all pregnant women should undergo a glucose screening for gestational diabetes, a simple prenatal test that involves drinking a sugary liquid and then having blood sugar levels checked.

Gestational diabetes usually goes away after the baby is born - and is manageable when caught and treated early - but many women with the condition may have it again with future pregnancies, and also have a higher risk of developing type 2 diabetes later.

Reviewed by: Steven Dowshen, MD
Date reviewed: February 2009

Source: "Maternal Overweight and Obesity and the Risk of Congenital Anomalies," JAMA, Feb. 2009.