Women who are obese before pregnancy are a third more likely to give birth to babies with certain birth defects than women of normal weight.

According to a study in the August issue of Archives of Pediatrics & Adolescent Medicine, those birth defects are:

1. Spina bifida, an opening in the spine.
2. Heart defects.
3. Malformation of the anal opening.
4. The urethra opening on the underside instead of the end of the penis.
5. Small or missing fingers, toes, arms or legs.
6. An opening in the diaphragm that permits abdominal organs to move into the chest cavity.
7. The intestines or other abdominal organs protruding from the navel.

The study was conducted by researchers at the University of Texas, Houston, on over 10,000 women in 8 states whose babies were born with birth defects between 1997 and 2002.

These women were compared to over 4,000 women who had babies without birth defects during the same time period.

Even with the increased risks from obesity, the number of babies born with birth defects is small. For obese mothers, birth defects occur in 4% of babies vs. 3% for women of normal weight.

The cause of these birth defects is unknown. But doctors suspect that undiagnosed Type 2 diabetes may play a role.