Exposure to agricultural pesticides in the first-trimester increases a woman’s risk of developing diabetes during pregnancy, research shows.

Previous studies have examined the relationship between pesticides and diabetes, the authors explain, but none have focused on pregnancy-related or “gestational” diabetes.

Dr. Tina M. Saldana from the National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina and colleagues assessed the risk of developing gestational diabetes following pesticide exposures among wives of farmers enrolled in the Agricultural Health Study.

Of 11,273 women who became pregnant within 25 years after entering the study, 506 (4.5 percent) reported having gestational diabetes.

Overall, 57 percent of women reported having mixed or applied pesticides at some time in their life, and the proportion was similar for those with and without gestational diabetes mellitus, the authors report in the journal Diabetes Care.

However, women who mixed or applied pesticides or repaired pesticide-related equipment during the first trimester of pregnancy had a more than twofold increased risk of developing gestational diabetes, the report indicates.

In contrast, there was no increased gestational diabetes risk among women with residential exposures to pesticides or indirect exposures during the first trimester.

Similarly, the researchers note, women who had mixed or applied pesticides at any time before enrollment in the study did not face an increased risk of gestational diabetes compared with those who did not.

Although much is known about common risk factors for pregnancy-related diabetes, “our understanding of whether and how environmental exposures may affect risk is still limited,” the authors conclude.

Understanding any potential effect of environmental exposures on glucose (sugar) tolerance during pregnancy “may have substantial public health importance beyond the direct effects on gestational diabetes.”

SOURCE: Diabetes Care, March 2007.