Association of birth outcomes with maternal and infant FADS1 rs174547 genotypes in Japanese participants.

N-3 long-chain polyunsaturated fatty acids (n-3LCPUFAs) are crucial for child growth and development particularly for fetal growth in utero and brain development and function. This study examined the relationship between birth outcomes and FADS1 rs174547 genotypes in Japanese mothers and infants. The study included 406 mothers and 373 infants, i.e., 373 infant-mother pairs, from a supplementary survey of the Japan Environment and Children's Study. Multiple regression analysis revealed that infants with the CC genotype had significantly smaller head circumference at birth compared to those with the TT genotype. Moreover, an interaction between infant genotype and cord blood docosahexaenoic acid (DHA; 22:6n-3) composition affected head circumference at birth. The findings suggest that maternal and infant FADS1 genotypes may influence fetal growth. Furthermore, in FADS1 genotype-stratified multiple regression analysis, infants with maternal and infant CC genotypes exhibited a significant positive association between head circumference at birth and maternal erythrocyte DHA/α-linolenic acid (ALA; 18:3n-3) ratio or fish intake. We highlighted lower metabolic efficiency for endogenous long-chain polyunsaturated fatty acids synthesis in infant-mother pairs homozygous for the minor C allele of FADS1 rs174547. In conclusion, for mothers and infants with this genetic background, maternal fish intake during pregnancy may be potentially important for fetal growth and development.