Many mothers-to-be are shocked to find they have developed gestational diabetes mellitus, or GDM, during their pregnancy. The condition is a serious complication of pregnancy, and pregnant women with GDM are at increased risk of developing elevated blood pressure, preeclampsia during pregnancy, and type-2 diabetes after pregnancy.

Women who develop GDM may wonder, “Why me? Did I drink too many sodas, eat too much ice cream, or chocolate?” Actually, potatoes could be partly to blame, according to a new study.

It is doubtful that a single food causes gestational diabetes, but pregnant women might want to be cautious about how often they eat potatoes in light of these findings.

Americans consume nearly 50 pounds of potatoes per person each year. They are considered a vegetable, and their consumption is encouraged as a way to meet guidelines for vegetable intake. But research has shown that potatoes can cause blood sugar levels to rise because they are high in starch.

This new study followed nearly 16,000 pregnant women who were part of the Nurses’ Health Study II between 1991 and 2001. None of the women had ever been diagnosed with GDM during a previous pregnancy or had any chronic disease prior to becoming pregnant.

Participants in the study completed food frequency questionnaires every four years, and researchers assessed potato intake from the previous year. Women self-reported a diagnosis of GDM.

Out of over 21,000 singleton pregnancies, there were 854 diagnoses of GDM. Once the researchers adjusted for other risk factors for the disease, like BMI and a family history of diabetes, they determined that a high intake of potatoes (as many as five servings a week) was associated with a higher risk of developing GDM, but substituting other vegetables, whole grains, or legumes for two servings of potatoes a week decreased the risk by 9 to 12 percent.

Compared to other vegetables, potatoes have a high glycemic index. This means the starch in potatoes is quickly absorbed by the body and can cause a sharp increase in blood sugar levels. The researchers, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development and Harvard University, believe this may be one explanation for the findings. Because the study was an observational one, it doesn’t prove that eating potatoes causes GDM.

It is doubtful that a single food causes gestational diabetes. Pregnant women might want to be cautious about how often they eat potatoes in light of these findings, but more importantly, they should pay attention to their entire diet, eat a wide variety of healthy foods, and keep their weight gain during pregnancy to a healthy level to reduce the risk of developing GDM.

The study is published in BMJ, The British Medical Journal.