Maternal plasma n-3 and n-6 polyunsaturated fatty acids during pregnancy and features of fetal health: Fetal growth velocity, birth weight and duration of pregnancy.

Key Findings:

Data from 6,974 pregnant women and their infants participating in the Generation R Study indicated that a higher maternal omega-3 to omega-6 ratio in mid-pregnancy was associated with a faster growth of the fetus, including weight, length and the head. A higher maternal n-3:n-6 PUFA ratio was associated with a better fetal health, determined by a higher fetal growth velocity from mid-pregnancy onward, a higher birth weight and a longer duration of pregnancy. These findings seem to be partly accounted for by higher percentage of maternal mid-pregnancy n-3 PUFA in glycerophospholipids, the major constituents of cell membranes. The close correlation between placental and birth weight illustrates the main importance of placental function for the growth and development of the fetus. As the placenta is an organ of extra-embryonic origin, the observed associations with placental weight might also reflect effects early in pregnancy. The patterns of the relationship of n-3 and n-6 PUFAs with placental weight are similar to findings with birth weight. Apart from maternal dietary intake, the fetal supply of fatty acids also depends on the fatty acid release from the maternal adipose tissue and the placental transport. Future research should address underlying pathophysiological mechanisms and the long-term effects on infant health.

ABSTRACT

BACKGROUND & AIMS: Maternal fatty acids are essential for fetal growth and development. Here, we examine associations between maternal mid-pregnancy plasma n-3 and n-6 polyunsaturated fatty acids (PUFAs) and fetal health determined by fetal growth velocity, birth weight and duration of pregnancy. METHODS: Participants were 6974 pregnant women and their infants from a population-based birth cohort, the Generation R Study. Maternal plasma n-3:n-6 PUFA ratio and n-3 and n-6 PUFA percentage in glycerophospholipids in mid-pregnancy were related to fetal growth velocity calculated from repeatedly measured weight, length and head circumference, birth weight, and duration of pregnancy. RESULTS:  A higher maternal mid-pregnancy n-3:n-6 PUFA ratio was associated with a higher growth velocity of the fetal weight (β = 0.082 SD-score/week, 95% CI 0.055; 0.108, P < 0.001), length (β = 0.085 SD-score/week, 95% CI 0.052; 0.119, P < 0.001); and head (β = 0.055 SD-score/week, 95% CI 0.019; 0.091, P = 0.003). We also observed positive associations between n-3:n-6 PUFA ratio and birth weight (β = 0.76 SD-score, 95% CI 0.22; 1.29, P = 0.006), and duration of pregnancy (β = 1.32 weeks, 95% CI 0.24; 2.40, P = 0.02). CONCLUSIONS: These results are consistent with the hypothesis that a higher n-3:n-6 PUFA ratio is important for fetal health.