Elevated insulin sensitivity and β-cell function during pregnancy in mothers of growth-restricted newborns

The "Barker hypothesis" suggests that low birth weight might predict future risk of developing obesity, cardiovascular disease, and type 2 diabetes. Identification of the causes of fetal growth restriction (FGR) is critical for preventive and management strategies. Some studies indicate that maternal carbohydrate metabolism might be involved in FGR development. We aimed to evaluate, in a large number of normotensive pregnant women with normal glucose tolerance, the effect of insulin sensitivity and β-cell function on unexplained fetal growth. A total of 1,814 Caucasian pregnant women with normal prepregnancy body mass index were tested with a 75-g, 2-h glucose load (24-28 gestation wk). Insulin sensitivity was evaluated with fasting (QUICKI) and dynamic index (OGIS) and β-cell function with a modified insulinogenic index as ΔAUC(insulin)/ΔAUC(glucose) and disposition index. FGR was a birth weight below the 5th percentile for gestational age. FGR developed in 99 (5.5%) pregnant women that showed significantly higher QUICKI, OGIS, insulinogenic, and disposition index with respect to women with normal-weight babies (P < 0.0001). By using multiple regression analysis in the FRG group, QUICKI and OGIS appeared as significant independent variables (P < 0.0001 and P < 0.0366, respectively). We conclude that elevated insulin sensitivity seems to be one of the factors involved in determining unexplained fetal growth retardation; its assessment, even only in the fasting state, could be useful to guide any possible monitoring and therapeutic strategies to reduce fetal complications.