Fetal and maternal plasma insulin-like growth factors and binding proteins in pregnancies with appropriate or retarded fetal growth

A prospective observational study of 104 women was performed to study whether the insulin-like growth factor (IGF) system in pregnancy before labour is associated with reduced fetal growth. Fetal blood was obtained by cordocentesis for prenatal diagnosis or at elective caesarean delivery and a maternal sample was also obtained. IGF-1 and IGF-2 and their binding proteins -1 and -3 were measured by RIA. The 35 cases were smaller than -2S.D.s by ultrasound abdominal circumference and birthweight and were subdivided into fetal growth retardation (FGR, n = 20) and small for gestational age (SGA, n = 15) by Doppler velocimetry and neonatal outcome. Controls (n = 69) were normally grown. Control maternal IGF-1 (r = 0.65, P < 0.0001) and IGFBP-3 (r = 0.46, P = 0.001) increased with advancing gestational age. In FGR cases, maternal IGF-1 was low (P = 0.0001) and IGFBP-1 was high (P = 0.03) and maternal IGF-2 was low in SGA (P = 0.005). In the SGA fetus, IGF-2 was low (P = 0.0009) and IGFBP-3 (P = 0.02) was high. In FGR, IGFBP-1 (P < 0.0001) and IGFBP-3 (P = 0.002) were both elevated. These data do not support the hypothesis that fetal IGF-1 deficiency is a common cause of FGR. Elevated binding proteins may lead to a relative deficiency of free IGF but changes in binding proteins may be secondary to metabolic changes. In FGR, maternal IGF-1 was low with high binding proteins, so this system may be important in controlling placental transfer.