Maternal plasma concentrations of insulin-like growth factor-I (IGF-I) and human placental lactogen (hPL) in twin pregnancies.

Maternal plasma IGF-I and hPL concentrations were examined in 10 singleton pregnancies and in 11 twin gestations near term. hPL concentrations were higher in the twin pregnancies (14.4 +/- 2.4 micrograms/l vs 6.9 +/- 0.9 micrograms/l, P less than 0.02). In contrast, plasma IGF-I concentrations were similar in the singleton and twin pregnancies (533 +/- 45 micrograms/l vs 572 +/- 60 micrograms/l, respectively). IGF-I concentrations failed to correlate with hPL concentrations in either group separately or when all subjects were considered together. These data do not support the hypothesis that maternal IGF-I secretion is an hPL-dependent process.