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Snacking on high GI foods during late pregnancy may lead to the birth of a heavier baby with an increased risk of childhood obesity, says new research

14 April 2009 University College Dublin (UCD)

Mothers who snack on high GI (Glycaemic Index) foods like chocolate and white bread during later pregnancy may give birth to heavier babies with a greater risk of childhood obesity, according to new research published in the British Journal of Obstetrics and Gynaecology.

The research by scientists from the UCD Conway Institute at University College Dublin, Ireland, and the National Maternity Hospital (NMH) in Dublin, Ireland, into sheep models of pregnancy discovered that high GI snack diets among ewes during the third trimester of pregnancy resulted in a heavier birth weight and postnatal growth rate of newborn lambs.

According to the scientists, the sheep model used in the scientific study is instructive of the relationship between a human mothers’ diet, the birth weight of their child, and the risk of childhood obesity. In previous scientific studies, the sheep model has been shown to share many elements of pregnancy with the human model including metabolic function and nutrient transport.

For the past 40 years, sheep models have been used to investigate maternal–fetal interactions in humans because sheep have a body weight of 65 to 85 kg, a 17 day (average) reproductive cycle, and they usually have 1 or 2 lambs per pregnancy with a relatively long gestation period of 147 days. Sheep models are also amenable to reproduction, nutritional and surgical manipulation and can tolerate observations like ultrasound and tissue collections such as blood sampling.

“For the first time, in a sheep model, the findings show that ewes fed high glycaemic foods twice daily in addition to their normal meals, during the last trimester of pregnancy, gave birth to heavier lambs with a faster postnatal growth rate,” says Professor Alex Evans, Associate Professor of Animal Physiology at the UCD School of Agriculture, Food and Veterinary Medicine, at University College Dublin, one of the co-authors of the study.

“Our findings show that maternal hyperglycaemia stimulates the production of insulin and suggest that this has a positive effect on fetal growth,” he explains. “Changing the source and pattern of intake of maternal dietary carbohydrate may help reduce maternal and fetal trauma at parturition and reduce the risk of obesity related diseases among offspring in later life.”

The new scientific research findings published in the British Journal of Obstetrics and Gynaecology will prompt further investigations into the effects of high-glycaemic diets during pregnancy on the birth weight of children and the associated potential future risk of developing childhood obesity. 

The Glycaemic Index (GI Index) is a scale of 0 – 100 which measures how a food raises blood glucose levels after it is eaten: dramatically, moderately or a little.

Higher GI values are given to foods that result in the most rapid rise in blood sugar once consumed. Many sweet and sugary foods have high GI but so too do starchy foods like potatoes and white bread. Glucose scores 100 on the GI Index, bananas score 52, and peanuts score 14. GIs of 70 or above are considered high, while GIs of 55 or below are considered low. Fish, pasta, milk, meat and most fruit and vegetables (except potatoes and watermelon) are low GI foods.

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