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.