Expectant mothers can reduce the risk of weight gain during pregnancy by switching to a high fibre diet, a study has found.
Maternity experts revealed that 400 mums-to-be, who changed their eating habits during the nine month term, put on an average of 1.5kg less than those who did not.
The study, carried out over several years at the National Maternity Hospital, found pregnant women could switch foods and maintain calorie intake without fear of putting on excess weight.
Professor Fionnuala McAuliffe, one of the study leads, said the low glycaemic index diet benefited a fifth of women.
"Our findings show that women who switch to a low GI diet during pregnancy are 20% less likely to experience excessive weight gain," she said. "This type of excessive weight gain during pregnancy is associated with an increased need for delivery by Caesarean section, a higher likelihood of post pregnancy weight retention, and a higher predisposition to obesity in later life."
Researchers said the best foods for the low glycaemic index (GI) diet are wholegrains, brown rice and bread. The GI ranks carbohydrates up to 100 according to their affect on blood sugar.
Low-GI food is slowly digested and has proven health benefits, including for weight control as they help control appetite and delay hunger.
The findings, published in the British Medical Journal (BMJ), monitored the weight and blood sugar of over 800 pregant women over several years.
Half of those studied were encouraged to maintain the normal quantity of foods eaten but to introduce more items with a low GI - with less sugar they are far less likely to be converted into fats by the body.
The remaining 400 women remained on pre-existing diets, which included foods such as white bread and rice and cornflakes.
The study found that the women on the low GI diet gained an average amount of 12.2 kg during pregnancy, while the remaining participants put on an average weight of 13.7 kg.
The research shows that women who maintain their diet had a 48% chance of excessive weight gain and those who switch to low GI a 38% chance.
Ms McAuliffe, professor of obstetrics and gynaecology at the University College Dublin School of Medicine, warned that extra pregnancy weight can lead to health problems for women.
She added: "Overall, the 400 women on the low GI diet during their pregnancy reported that the diet was easy to follow and to shop for, and 80% said that they followed the diet all or most of the time."