Relationship between amniotic fluid insulin and maternal blood glucose concentrations in patients with carbohydrate intolerance during pregnancy

In contrast to maternal blood glucose, amniotic fluid insulin (AFI) directly reflects the functional state of the fetal pancreas. In a prospective study we evaluated the correlation of AFI with maternal metabolic control in 70 amniotic fluid specimens from 61 women having carbohydrate intolerance during pregnancy (White A n = 44, B0 n = 17). AFI was measured with the Insulin RIA 100 kit from Pharmacia (Freiburg). The normal range of AFI was established in 304 healthy pregnant women (16th-42nd gestational week). AFI concentrations increased by a factor of 1.5 to 2 during gestation reflecting the maturation of the fetal pancreas. Elevated AFI levels (> 97th centile) were found in 11% of normoglycemic diabetics and in 500% of women with insufficient metabolic control. Despite a high overall concordance (81%) no direct relationship could be found between fetal and maternal parameters. Patients with increased AFI values had a 5-fold higher rate of large-for-gestational age (LGA) infants than women with normal levels. This finding confirms the pathogenetic role of hyperinsulinism in the development of fetal macrosomia.