The Objective of this paper is to determine the relation between fetal macrosomia in offspring of nondiabetic women, and the levels of insulin-like growth factors (IGF-I, IGF-II), insulin growth factor binding protein-3 (IGFBP-3) and insulin, in maternal and neonatal compartments. Serum samples were obtained from normal pregnant women (n = 60) and their neonates (n = 60) between 37-41 weeks' gestation (mean 39 ± 9). Neonates were categorized as appropriate for gestational age (AGA; 10th-90th percentile; n = 20), and large for gestational age (LGA; >90th percentile; n = 40). Maternal and neonatal serum samples were analyzed for levels of IGF-I, IGFII, IGFBP-3 and insulin, by specific radioimmunoassays (RIAs). Serum levels were correlated with birth weight. The mean birth weight of the AGA group was 3296 ± 500 g versus 4201 ± 300 g for the LGA group (p <0.0001). Cord blood IGF-I was statistically higher in LGA group than in the AGA infants, (139 ± 67 ng/mL and 80 ± 32 ng/mL, respectively; p <0.0001). There was no correlation between maternal IGF-I serum levels and birth weight (363 ± 131 in the AGA vs. 308 ± 158 in the LGA group). IGF-II in maternal and cord blood did not correlate with fetal weight. Cord blood IGFBP-3 was significantly higher in the LGA group (1.1 ± 0.07 μg/mL) than in the AGA group (0.96 ± 0.05 μg/mL; p <0.05). Maternal insulin levels were similar between the two groups. Neonatal insulin levels were higher in the LGA group (18 ± μU/mL) as compared to the AGA group (16 ± μU/mL), however, this difference did not reach statistical significance. Fetal cord blood levels of IGF-I and IGFBP-3 are directly correlated with the birth weight of large for gestational age fetuses. These data suggest that the somatotropic axis plays a role in fetal growth. Additionally, insulin growth factor-1 appears to be an in utero growth promoter in the development of fetal macrosomia in infants of nondiabetic women.
- LGA infants