Maternal obesity linked to birth defects

Mothers of babies born with some structural birth defects - including missing limbs, malformed hearts and underdeveloped spinal cords - appear more likely to be obese prior to becoming pregnant than mums whose children are born without such defects, according to the report in the August issue of Archives of Pediatrics & Adolescent Medicine.

University of Texas researchers studied more than 10,000 mothers of babies with birth defects and compared them to mothers of healthy children. They found that obesity was linked to an increased risk of seven out of 16 types of birth defects. Those children had a 40% increased risk for heart defects and more than double the odds of spina bifida.

The causes behind the birth defects are unknown, but doctors suspect that the higher rates of diabetes in obese mothers may play a role.

"Our study supports previous evidence as well as provides new evidence for the associations between maternal obesity and particular categories of birth defects," the authors conclude. "Future inquiries are needed to unravel the underlying reasons for these associations."

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

"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.