High consumption of potatoes before pregnancy is linked to a significantly higher risk of gestational diabetes, according to new research.

The study, conducted by researchers from the National Institutes of Health, examined data from more than 15,000 women, taken from the Nurses’ Health Study, 1991-2001. None of the women had a history of gestational diabetes or any other chronic disease.

Every four years, the women reported their intake of potatoes, and also any diagnoses of gestational diabetes they had received from a physician. Of the 21,693 singleton pregnancies (that is, pregnancies that involved only one child) there were 854 cases of gestational diabetes.

The researchers observed a significant and positive link between high potato consumption and gestational diabetes. Women who ate one serving per week were 20 per cent more likely to develop gestational diabetes. Two to four portions increased the risk by 27 per cent, and five or more raised the risk by 50 per cent.

However, the findings do not necessarily indicate that potatoes cause the increased risk. Rather, there is a correlation between women who eat a lot of potatoes before pregnancy and their risk of gestational diabetes. Further studies are required to determine whether potatoes are in fact the cause.

“In summary, in this large prospective cohort study, pre-pregnancy potato consumption was significantly and positively associated with the risk of incident GDM,” the researchers wrote. “Substitution of potatoes with other vegetables, legumes, or whole grain foods was associated with a lower risk of GDM. These findings should be confirmed in intervention studies and randomised controlled trials.”

The findings are published in the BMJ.