Association of intake of trans fatty acids in the 2nd trimester of pregnancy with risk of preeclampsia was studied by following 67 186 pregnancies of women participating in the Danish National Birth Cohort between 1998 and 2003. Diet was assessed with a food frequency questionnaire at gestation wk 25; preeclampsia diagnosis was obtained by linkage with the Danish National Patient Registry. 1804 cases of preeclampsia and 402 cases of severe preeclampsia were identified in the cohort. Intake of trans fats decreased during the study period as a consequence of reduction in industrial trans fat intake. Intake of trans fats in the 2nd trimester was unrelated to risk of preeclampsia or severe preeclampsia. Relative risk (95% confidence interval; P, trend) of preeclampsia and severe preeclampsia comparing top to bottom quintiles of trans fat intake were 0.95 (0.81; 1.11, 0.33) and 1.07 (0.78; 1.48, 0.92), respectively. It is concluded that 2nd trimester intake of trans fats is unrelated to risk of preeclampsia within the intake range observed in a period of gradual reduction of industrial trans fats from the Danish food supply.