Chicago ? Women who are obese before pregnancy face a higher risk of having babies with a variety of birth defects than women with a healthy weight, a new study suggests.

The results involving nearly 15,000 women from eight states found abnormalities of the spine, heart, arms, legs and abdomen, building on previous research that showed heart and spine defects. The greatest risk was for spina bifida.

“Obese women should not be overly alarmed by these findings because their absolute risk of having a child with a birth defect is low, and the cause of the majority of birth defects is unknown,” said University of Texas researcher Kim Waller, the study’s lead author.

Still, the results underline yet another reason for women to maintain a healthy weight, Waller said.

The findings suggest that about 4 percent of women who are obese before pregnancy will have babies with major birth defects, versus 3 percent for healthy-weight women, Waller said.