Pre-pregnancy potato consumption and risk of gestational diabetes mellitus: prospective cohort study

STUDY QUESTION What is the association between potato consumption before pregnancy and the risk of gestational diabetes mellitus (GDM)? METHODS This prospective cohort study included 15,632 women from the Nurses' Health Study II (1991-2001). They had no previous GDM or chronic diseases before pregnancy. Consumption of potatoes and other foods was assessed every four years. Incident first time GDM was ascertained from self reports of a physician diagnosis of GDM, which was previously validated by medical records. STUDY ANSWER AND LIMITATIONS Over the 10 year follow-up there were 854 incident cases of GDM among 21,693 singleton pregnancies. After adjustment for age, parity, and dietary and non-dietary factors, women who consumed more potatoes before pregnancy had higher rates of developing GDM. Substitution of two servings a week of total potatoes with other vegetables, legumes, and whole grain foods was significantly associated with a 9-12% lower risk of GDM. Consumption and diabetes were self reported, and severity of diabetes was unknown. More than 90% of women were white. A causal association cannot be assumed. WHAT THIS PAPER ADDS Higher levels of potato consumption before pregnancy are associated with greater risk of GDM, and substitution of potatoes with other vegetables, legumes, or whole grain foods might lower the risk. FUNDING, COMPETING INTERESTS, DATA SHARING Funding was received from the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institutes of Health, and the American Diabetes Association (No 7-12-MN-34). The authors have no competing interests or additional data to share.