Familial aggregation of fetal growth restriction in a French cohort of 7,822 term births between 1971 and 1985

An association between fetal growth restriction and increased rates of metabolic and cardiovascular diseases in adulthood has been reported. This study evaluated familial aggregation of fetal growth restriction in term births. The population consisted of 3,505 sibships comprised of 7,822 full-term singleton infants born between 1971 and 1985 in Haguenau, France, and selected from a regional register of births. Sib-sib odds ratios were estimated for being born small for gestational age (SGA), defined as having a birth weight below the 10th percentile of the sex-specific curve of birth weight by week of gestation. SGA births were further stratified according to ponderal index (birth weight/length(3)). After adjustment for maternal factors, the sib-sib odds ratios were 4.8 (95% confidence interval (CI): 3.7, 6.3) for all SGA births, 7.7 (95% CI: 4.1, 14.7) for SGA births with a low ponderal index (<10th percentile), and 4.4 (95% CI: 2.3, 8.2) for SGA births with a normal ponderal index (25th-75th percentile). None of the maternal factors investigated significantly influenced the magnitude of these odds ratios. This strong residual sib-sib aggregation suggests a role for genetic and/or shared environmental factors in the etiology of fetal growth restriction, especially when associated with a low ponderal index.