Alterations in circulating human chorionic gonadotropin free alpha-subunit in insulin-dependent diabetic pregnancy: correlation with maternal characteristics

Abstract

Circulating concentrations of hCG free alpha-subunit (alpha hCG) increase throughout pregnancy. To address the hypothesis that maternal plasma alpha hCG may reflect placental dysfunction and/or adverse perinatal outcome during insulin-dependent diabetic pregnancy, alpha hCG was measured serially throughout gestation, beginning before week 12, with a specific RIA using a monoclonal antibody in 54 insulin-dependent diabetic (randomly assigned to strict and customary glycemic control) and 25 nondiabetic pregnancies. alpha hCG was significantly lower in pregnant insulin-dependent diabetic subjects than in nondiabetics subjects until 24 weeks gestation, after which it was higher until delivery. Plasma alpha hCG stabilized in nondiabetics at 32 weeks, whereas it continued to increase in diabetics until delivery, at which time it was 37% greater than that in nondiabetics (mean +/- SE, 1441 +/- 90 vs. 1052 +/- 78 micrograms/L; P less than 0.002). Values in diabetic subjects assigned to strict control were intermediate between those in diabetic subjects assigned to customary control and nondiabetic subjects. alpha hCG was greater in diabetic subjects with pregestational hypertension or microvascular disease, but not in those with pregnancy-induced hypertension. These findings were independent of the assigned goals of glycemic control. alpha hCG was not correlated with the duration of diabetes or related to premature delivery, fetal distress, birth asphyxia, or macrosomia. Thus, alpha hCG is increased during the third trimester of the type I diabetic pregnancy and is associated with preexisting hypertension and maternal microangiopathy, but is not a predictor of adverse perinatal outcome. Excessive alpha hCG secretion in diabetes may share pathophysiological mechanisms in common with those underlying diabetic microangiopathy.