Background: The purposes of this study were to explore whether serum levels of insulin, insulin-like growth factor-I (IGF-I), insulin-like growth factor-binding protein-1 (IGFBP-1) and IGFBP-3 in both maternal and fetal compartments were affected by the stress of labor, and to investigate the relationship between the fetal birthweight and serum levels of insulin, IGF-I and IGFBPs.
Methods: Blood samples were collected at the time of delivery from 147 parturients with vaginal delivery and 128 cases of Cesarean section (112 cases without labor and 16 cases with arrest of cervical dilatation during the active phase of labor). Serum concentrations of insulin, IGF-I, IGFBP-1 and IGFBP-3 were determined by radioimmunoassays (insulin, IGFBP-1 and IGFBP-3) and immunoradiometric assay (IGF-I).
Results: Maternal circulating IGFBP-1 levels in parturients with normal spontaneous delivery (NSD) and in subjects receiving Cesarean section (CS) due to arrest of cervical dilatation during active phase of labor were higher than those undergoing scheduled CS without labor. By contrast, insulin levels in both maternal and umbilical cord serum were higher in parturients with CS without labor than those with NSD. No difference in maternal serum IGFBP-3 levels was observed between NSD and CS at the time of delivery. As for all measurements (insulin, IGF-I, IGFBP-1 and IGFBP-3), serum levels in pregnant women (from both NSD and CS) were strikingly higher than those in the fetus. Serum levels of IGFBP-1 in umbilical cords from both groups of NSD (p < 0.02) and scheduled CS (p < 0.01) were inversely correlated with birthweight (BW). By contrast, serum concentration of insulin and IGF-I in umbilical cords from NSD (p < 0.005 and p < 0.01; respectively) and scheduled CS (p < 0.01 and p < 0.05; respectively) were positively related to BW.
Conclusions: From the present results, we conclude that insulin appears to be a regulator for circulating IGFBP-1 during pregnancy. The fetal growth may not be well reflected by maternal serum IGFBP-1 levels, nor by IGFBP-3. By contrast, cord serum IGFBP-1 from CS group without labor may preeminently reflect fetal weight. In additional, serum concentration of insulin and IGF-I in umbilical cord may also be good indicators to reflect the result of neonatal birthweight.