... While some research has suggested that obese women have an increased risk of having a baby with a birth defect, a new study shows that diabetes may at least partly account for the link.
Studies on whether obesity raises the odds of birth anomalies such as spina bifida, cleft palate and heart defects have so far come to conflicting conclusions. One question is whether obesity, per se, is the problem -- or whether certain factors associated with obesity are at work.
Type 2 diabetes, which is closely related to obesity, has been linked to a heightened risk of birth defects in a number of studies.
The new study ... found no association between mothers' obesity and the risk of any major birth defect. However, there was a link seen with diabetes.
Women who'd had diabetes before becoming pregnant showed a nearly four-fold higher risk of having a baby with a birth defect than women without the disorder.
... The vast majority of babies in the study were born with no congenital defects; across the study period, the rate of any major anomaly was less than 1 percent among all women.
... past research has shown that well-controlled diabetes carries a lesser risk.
... Based on that evidence, diabetic women who are thinking about pregnancy should try to optimize their blood sugar control ...
There are several theories on why diabetes is related to birth defects ... Excess blood sugar ... is delivered to the embryo early in pregnancy, and that may end up spurring an overproduction of cell-damaging substances called free radicals. The extra sugar may also result in metabolic byproducts that interfere with signaling mechanisms critical to embryonic development, Biggio noted.