Plasma phospholipid polyunsaturated fatty acids composition in early pregnancy and fetal growth trajectories throughout pregnancy: Findings from the US fetal growth studies-singletons cohort.

Background: We aimed to investigate plasma phospholipid PUFA levels in early pregnancy and fetal growth trajectories throughout pregnancy.

Methods: Within the NICHD Fetal Growth Studies-Singleton Cohort, we enrolled 2,802 pregnant women at gestational weeks 8-13 and randomly assigned them to four ultrasonogram schedules to capture weekly fetal growth throughout pregnancy. Eleven plasma phospholipid PUFAs were measured at early pregnancy using blood samples collected from a subsample of 321 pregnant women. We modeled fetal growth trajectories across tertiles of PUFAs with cubic splines using linear mixed models after adjusting for major confounders. We then compared pairwise weekly fetal growth biometrics referencing the lowest tertile in each PUFA using the Wald test.

Findings: Among plasma n-3 PUFAs in early pregnancy, docosahexaenoic acid (DHA, 22:6n3) and alpha-linolenic acid (ALA, 18:3n3) showed positive associations with all fetal growth measurements. For instance, compared with the lowest tertile, the highest tertile of DHA had greater estimated fetal growth (EFW) and abdominal circumference (AC), starting at 13 weeks of gestation and throughout pregnancy (at gestational week 38: 3235.3 vs. 3089.0 g for EFW; 344.6 vs. 339.2 mm for AC). As for plasma n-6 PUFAs, some showed positive associations (e.g., linoleic acid [LA], 18:2n6) while others (e.g., docosatetraenoic acid [DTA], 22:4n6) showed inverse associations with fetal growth measures.

Interpretation: Our data suggested that higher plasma levels of DHA and ALA in the first trimester were associated with increased fetal size and weight throughout subsequent pregnancy.

Funding: National Institute of Child Health and Human Development intramural funding.