Eating more potatoes, including French fries and potato chips, before pregnancy may be associated with greater risk of gestational diabetes mellitus, according to a study published online ahead of print January 12 in the British Medical Journal.

Senior author Cuilin Zhang, MD, MPH, PhD, and fellow investigators suggested that patients who are trying to conceive may lower their risk of gestational diabetes by substituting potatoes with other foods. “Higher levels of potato consumption before pregnancy are associated with greater risk of gestational diabetes mellitus,” they wrote, “and substitution of potatoes with other vegetables, legumes, or whole grain foods might lower the risk.”

The researchers followed a cohort of 15,632 women from the Nurses’ Health Study II from 1991 to 2001. More than 90% of the subjects were white. Over 10 years, there were 854 cases of gestational diabetes among 21,693 women with singleton pregnancies. The investigators found that women who consumed more potatoes before pregnancy had higher rates of developing gestational diabetes and that substituting two servings of potatoes with other vegetables, legumes, and whole grain foods each week was significantly associated with a 9% to 12% lower risk.

The findings may be explained in part by the high glycemic index associated with potatoes, which can result in a sharp rise in blood sugar levels after consumption, according to the authors.