Maternal trans fatty acid intake and fetal growth.

Background: It is unclear from previous studies whether total or common subtypes of trans fatty acids are associated with fetal growth.

Objective: We examined associations of maternal trans fatty acid intake during pregnancy with fetal growth.

Design: We studied 1369 mother-child pairs participating in Project Viva-a prospective cohort study of pregnant women and their offspring. We assessed trans fatty acid consumption by using a validated semiquantitative food-frequency questionnaire in each of the first and second trimesters of pregnancy. We estimated fetal growth as the birth-weight-for-gestational-age (BW/GA) z value in infants born at term.

Results: We observed no associations of first-trimester trans fatty acid consumption with fetal growth. In the second trimester, the estimated mean (±SD) total trans fatty acid intake was 2.35 ± 1.07 g/d, of which 0.11 g was 16:1(n-7t), 1.78 g was 18:1(n-9t), 0.13 g was 18:2(n-6tt), 0.33 g was 18:2(n-6tc), and 0.12 g was 18:2(n-6ct). The mean (±SD) BW/GA was 0.24 ± 0.95 z score units. Total trans fatty acid consumption during the second trimester was positively associated with the fetal growth z score (0.29 units; 95% CI: 0.07, 0.51 units) for each 1% increment in energy from trans fatty acids as a replacement for carbohydrates. The associations were limited to the trans fatty acids 16:1t (0.12 units; 95% CI: 0.02, 0.22 units) and 18:2tc (0.53 units; 95% CI: 0.09, 0.96 units).

Conclusion: A higher maternal intake of trans fatty acids, especially 16:1t and 18:2tc, during the second trimester of pregnancy was associated with greater fetal growth.