Eating potatoes or chips on most days of the week may increase a woman's risk of diabetes during pregnancy, US researchers have claimed.
They argue that this is because starch in potatoes can trigger a sharp rise in blood sugar levels.
Their study - featured in the BMJ - tracked more than 21,000 pregnancies.
UK experts have fought back, though, and stated that proof is lacking, and that lots of people need to eat more starchy foods for fibre, as well as fresh fruit and veg.
The BMJ study linked high potato consumption to a higher diabetes risk.
Swapping a couple of servings a week for other vegetables should counter this, the authors argued.
UK dietary advice says starchy foods (carbohydrates) such as potatoes should make up about a third of the food people eat.
There is no official limit on how much carbohydrate people should consume each week.
The study set out investigate what might make some women more prone to pregnancy diabetes. It followed nurses who became pregnant between 1991 and 2001. None of them had any chronic diseases before pregnancy.
Every four years, the women were asked to provide information on how often potatoes featured in their diets, and any cases of gestational diabetes were noted.
Over the 10-year period, there were 21,693 pregnancies and 854 of these were affected by gestational diabetes.
The study took into account other risk factors, such as age, a family history of diabetes, overall diet, physical activity and obesity.
It found a 27 per cent increased risk of diabetes during pregnancy in the nurses who typically ate two to four 100g (3.5oz) servings of boiled, mashed, baked potatoes or chips a week.
In those who ate more than five portions of potatoes or chips a week, the risk went up by 50 per cent.
The researchers estimate that if women swap their potatoes for vegetables or whole grains at least twice a week, they could lower their diabetes risk by 9 to 12 per cent.