OBJECTIVE: To evaluate whether low intakes in pregnancy of marine n-3 fatty acids or calcium increase the risk of preeclampsia, pregnancy induced hypertension, intrauterine growth retardation, or preterm delivery and whether high intakes of the above nutrients increase the risk of postterm delivery.

DESIGN: A case-control nested in cohort study.

SUBJECTS AND METHODS: Between 1989 and 1991 a cohort of 9,434 pregnant women was established. Forty-three preeclamptics, 179 women with pregnancy induced hypertension, 182 with intrauterine growth retardation, 153 delivering preterm, and 189 delivering postterm together with 256 controls were sampled for this study. Dietary information was obtained retrospectively between six months and 3 1/2 years after delivery using a semiquantitative food frequency questionnaire, whilst information on potential confounders was obtained from the cohort data base and analyzed by multiple logistic regression. Questions regarding marine n-3 fatty acids and calcium intake provided the basis for categorization into three and five intake groups respectively.

RESULTS: For all five pregnancy outcomes and both nutritional factors, none of the confounder-adjusted odds ratios comparing higher intake levels with the lowest intake level were significant. Neither were chi 2-tests for trend calculated for each pregnancy outcome statistically significant (p > 0.20). Odds ratios for highest versus lowest intake levels were for n-3 fatty acids 0.79 ((0.27 to 2.34 (95% CI)) for pregnancy induced hypertension, 1.00 (0.34 to 2.95) for intrauterine growth retardation, and 0.99 (0.35 to 2.74) for preterm delivery; for calcium they were 0.92 (0.33 to 2.60) for pregnancy induced hypertension, 0.77 (0.25 to 2.42) for intrauterine growth retardation, and 1.05 (0.36 to 3.10) for preterm delivery.

CONCLUSIONS: No associations could be detected in these data between calcium or fish intake and adverse pregnancy outcome.