Maternal and fetal insulin-like growth factors and their binding proteins in the second and third trimesters of human pregnancy.

The insulin-like growth factors (IGFs) are mitogenic polypeptides which circulate bound to a series of at least six binding proteins (IGFBPs). An increasing body of evidence supports a major role for the IGF in the control of human fetal growth although normal values in the human fetal circulation have not been established. In order to provide an accurate reflection of fetal IGFs and IGFBPs in utero, we have sampled fetal blood direct from the umbilical cord at 18-38 weeks of gestation using the technique of cordocentesis. We have measured IGF-I, IGF-II and IGFBP 1-3 in 91 fetuses in order to establish concentrations for these parameters in the second and third trimesters of human pregnancy.