Cord blood level of insulin-like growth factor-1 and IGF binding protein-3 in monochorionic twins.

BACKGROUND/PURPOSE: Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are known to modulate fetal growth but their role in intrauterine growth of monochorionic twins (MCT) has not been studied. METHODS: Cord venous blood was collected directly after birth. IGF-1 and IGFBP-3 in the cord venous blood were quantified by radioimmunoassay. Birth weights (BWs) were obtained electronically. Placentas were examined for chorionicity. RESULTS: Cord blood was collected in 37 pairs of MCT (15 pairs were males). BWs ranged from 564 to 3240 g, and gestational ages (GAs) were between 24 weeks and 39 weeks. There was a correlation between BW and cord venous blood IGFBP-3 concentration (r = 0.28, p = 0.015), but not between BW and cord venous blood IGF-1 level. There was no difference in IGF-1 between the heavier twins (30.8 ± 61.8 ng/mL) and lighter twins (33.2 ± 63.7 ng/mL), but a trend (p = 0.096) of higher IGFBP-3 level was demonstrated in heavier twins (3.14 ± 1.23 µg/mL) than in lighter twins (2.71 ± 1.19 µg/mL). The IGFBP-3 levels were higher (p = 0.042) in female twins (3.20 ± 1.33 µg/mL) than in male twins (2.64 ± 1.04 µg/mL). The IGF-1 level of the heavier twins correlated significantly to their lighter co-twin (r = 0.73, p < 0.001). CONCLUSION: Our data showed that cord venous blood IGF-1 level might be controlled mainly by genetic factors. IGFBP-3 might play an important role in fetal growth.