Variation in the IGF1 gene and growth in foetal life and infancy. The Generation R Study

Objective The objective of this study was to examine whether variants of the IGF1 gene are associated with growth patterns from foetal life until infancy. Study design and measurements This study was embedded in the Generation R Study, a population‐based prospective cohort study of foetal life. Foetal growth (head circumference, abdominal circumference, femur length, estimated foetal weight) was assessed by ultrasound in early, mid‐ and late pregnancy. Growth in infancy was assessed at birth (weight) and at the ages of 6 weeks, 6 months and 14 months (head circumference, length, weight). The IGF1 promoter region genotype was determined in 738 children. Results Eight alleles of the IGF1 promoter region were identified. In total, 43% of the subjects were homozygous for the most common 192‐bp allele (wild‐type), 45% were heterozygous, and 12% were noncarriers of the 192‐bp allele. No differences were found in birthweight between the three groups. However, noncarriers had a lower estimated foetal weight in mid‐pregnancy (P = 0·040), followed by an increased growth rate until 6 months (P < 0·005) in comparison to the 192‐bp homozygotes. A similar difference in growth rate was found for length (P < 0·001). Conclusions Variants of the IGF1 promoter region are not associated with birthweight. However, noncarriers of the 192‐bp allele tend to have a smaller foetal size, followed by an increased growth rate from mid‐pregnancy to early infancy. Studies in larger cohorts are necessary to replicate our findings and to examine whether these effects persist throughout childhood.