Insulin sensitivity in third trimester pregnancy. A randomized study of dietary effects.

The metabolic effects of three diets were investigated in a randomized study in 15 non-pregnant women and 14 pregnant women in the third trimester; all the women were of normal weight. After 2-week periods of habituation to each diet, metabolic profiles were performed on standardized intakes. Diet 1 contained 40% of energy as carbohydrate and 10 g dietary fibre representing typical Western intakes. Diet 2 contained 40% energy as carbohydrate and 52 g dietary fibre and diet 3 contained 60% of energy as carbohydrate and 84 g dietary fibre, representing typical developing world intakes. No deterioration in glucose homeostasis in pregnancy was seen on any of the three diets in contrast to previous work. On diet 1 there was a loss of insulin sensitivity in pregnancy, but not on diets 2 and 3. The loss of insulin sensitivity which is typical of Western women in the third trimester of pregnancy and is considered to be physiological, may be a diet-induced artefact.