Eating sugary or highly processed foods during pregnancy may increase the risk of birth defects, research suggests.
Cornflakes may have a downside
US researchers compared the diet of 454 mothers of children with neural tube defects like spina bifida, with 462 mothers who had healthy babies.
They found the risk of defects doubled in women who ate lots of foods which give a quick sugar hit - and among obese women it quadrupled.
The research is published in the American Journal of Clinical Nutrition.
The researchers, from the University of California, focused on foods that have a high glyacemic index (GI).
This means that they release large amounts glucose into the blood very quickly, giving a sugar rush, followed by a low.
Examples of high GI foods include corn flakes, potatoes, cooked carrots, white bread, white rice, chocolate biscuits, honey and some soft drinks.
Scientists believe that the sudden release of large amounts of glucose may interfere with the development of babies in the womb - in particular the formation of the tube of bone around the spinal column.
Low GI foods, which give a slow release of glucose, include green vegetables, fresh fruit, wholegrain cereals and whole-wheat pasta.
Andrew Russell, chief executive of the Association for Spina Bifida and Hydrocephalus, told BBC News Online that the research should be treated with caution until further studies backed up the findings.
He said: "Neural tube defect research is very complicated, and theories around about the significance of sugars, proteins, vitamins and other micronutrients.
"The idea that a sugar surge in the maternal blood could cause spina bifida, while not impossible, would need quite a lot of corroboration because there are so many other things that feed into the metabolic process which controls development and closure of the spinal column.
"I would not feel at all comfortable about telling a mother that because she ate a cream bun in the early stages of pregnancy she was responsible for her child's lifelong disability."
Mr Russell said the vitamin Folic Acid had been shown to play a crucial role in the this process.
Research from Oxford Brookes University, published earlier this month, found children who eat a high-GI breakfast cereal get hungrier before lunchtime, and are more likely to snack and eat more calories overall.
A spokesman for Kellogg's, which makes corn flakes and other high GI cereals, said: "The science is relatively new and in some areas controversial.
"There is clear evidence that foods such as Kellogg's Corn Flakes, which are high in carbohydrate and low in fat, play an important role in helping people reduce fat intakes, maintain weight levels and possibly help their bodies to better control blood sugar levels."