Insulin-like growth factor 2 (IGF2) and IGF2 receptor gene variants are associated with fetal growth

Aim: Normal variation in size at birth is a result of the interaction between fetal genetic factors and the maternal uterine environment. It is, however, unclear how genetic factors contribute to fetal growth. The insulin-like growth factor (IGF) system regulates uterine, placental and fetal development, thereby partially controlling the rate of fetal growth. The aim of this study was to investigate the associations between the neonatal birth weight and the genotypes of polymorphic loci in the IGF2 and IGF2 receptor (IGF2R) genes. Methods: We determined the genotypes of two polymorphic loci in the IGF2 gene and four loci in the IGF2R gene in 884 pairs of normal Japanese mothers and their neonates, and compared the genotypes with the birth weight converted into standard deviation scores (SDSs) according to sex, parity and gestational weeks at delivery. Results: There was a significant difference in birth weight SDSs among the three neonatal +3123/ApaI genotypes of the IGF2 gene; AA, AG and GG. There was also a significant difference in birth weight among the three neonatal c.901C > G genotypes of the IGF2R gene; CC, CG and GG. Conclusion: These findings indicate that both IGF2 and IGF2R gene variants are associated with fetal growth.