Somatomedin-like activity, prolactin, growth hormone and insulin in human cord blood.

In order to assess the possible influence of fetal polypeptide hormones on birth size, somatomedin-like receptor activity (SmLRA) (n = 281), prolactin (n = 158), growth hormone (n = 133) and insulin (n = 108) concentrations were measured in the cord blood of 281 singleton infants born after different complications of pregnancy. Infant sex did not significantly affect the concentration of any hormone. SmLRA concentrations appeared to rise from 25 to 38 weeks of gestation, but thereafter fell. Concentrations of prolactin, growth hormone and insulin correlated negatively with gestational age. Insulin emerged as the hormone most clearly related to fetal growth, since concentrations were high (mean +/- SD = 20.6 +/- 11.5 uU/ml) in serum from infants of diabetic mothers (IDM) and other large-for-dates infants (10.1 +/- 4.8 uU/ml), but low (5.3 +/- 0.5 uU/ml) in infants who were small-for-dates (SFD). In contrast, SmLRA concentrations were high in serum from SFD infants (0.63 +/- 0.29 U/ml) and low in IDM (0.43 +/- 0.16 U/ml). Prolactin concentrations were higher in serum from SFD infants (212 +/- 101 ng/ml) and from IDM (237 +/- 182 ng/ml) than from normal infants born at term (139 +/- 68 ng/ml). Administration of intramuscular betamethasone to pregnant women in premature labour resulted in significant elevations in the concentrations of prolactin and insulin in cord blood.