The insulin-like growth factor-I (IGF-I) gene in individuals born small for gestational age (SGA)

To investigate the association of genetic variation of the insulin-like growth factor-I (IGF-I) gene with birth size small for gestational age (SGA).

We have studied a cohort of 120 SGA patients and 147 appropriate for gestational age (AGA) controls from Haguenau, France.

PCR-SSCP analysis was performed to detect sequence variation in the coding region of the IGF-I gene. Microsatellite markers near the IGF-I gene (intronic and D12S78) were selected and amplified to perform further analysis by association studies.

A novel polymorphism in intron 2 was discovered, but allele-specific PCR analysis in the 120 SGA patients and 147 AGA controls found no association between this polymorphism and birth size SGA. Chi squared (chi2) analysis found no statistically significant association between the allele distribution of the microsatellite markers in the SGA subjects and the AGA controls. Power calculations estimate that the D12S78 marker has an 80% chance of detecting a 10-15% difference.

These studies suggest that genetic variation of IGF-I alone does not result in birth size small for gestational age in this population. Thus, if this gene influences fetal size, it plays only a minor role in a multifactorial disorder which involves other genetic and environmental factors.