Maternal n-3, n-6, and trans fatty acid profile early in pregnancy and term birth weight: a prospective cohort study.

Background: Maternal n-3, n-6, and trans fatty acids are claimed to affect fetal growth, yet evidence is limited.

Objective: We investigated the association between maternal n-3, n-6, and trans fatty acids measured early in pregnancy and fetal growth.

Design: Amsterdam pregnant women (n = 12 373) were invited to complete a questionnaire (response 67%) and donate blood around the 12th pregnancy week for nutrient analysis. For 4336 women, fatty acid concentrations were measured in plasma phospholipids (gas-liquid chromatography). Associations of these concentrations with birth weight and small-for-gestational-age (SGA) risk were analyzed (liveborn singleton term deliveries, n = 3704).

Results: Low concentrations of individual n-3 fatty acids and 20:3n-6, the precursor of arachidonic acid (20:4n-6), but high concentrations of the other n-6 fatty acids and the main dietary trans fatty acid (18:1n-9t) were associated with lower birth weight (estimated difference in univariate analysis -52 to -172 g for extreme quintile compared with middle quintile). In general, SGA risk increased accordingly. After adjustment for physiologic, lifestyle-related and sociodemographic factors, low concentrations of most n-3 fatty acids and 20:3n-6 and high concentrations of 20:4n-6 remained associated with lower birth weight (-52 to -57 g), higher SGA risk, or both (odds ratios: 1.38-1.50). Infants of the 7% of women with the most adverse fatty acid profile were on average 125 g lighter and twice as likely to be small for gestational age.

Conclusion: An adverse maternal fatty acid profile early in pregnancy is associated with reduced fetal growth, which, if confirmed, gives perspective for the dietary prevention of lower birth weight.