To investigate associations of maternal periconceptional shellfish, lean fish and fatty fish intake with risk of pregnancy complications.

In this prospective cohort study, we collected information on intake of seafood subtypes using FFQ. We categorized seafood intake into frequencies of <0·2 servings/month, 0·2 servings/month–<0·5 servings/week, 0·5–1·0 servings/week and >1 servings/week. We ascertained gestational hypertension, pre-eclampsia, gestational diabetes and preterm birth diagnoses from medical records. Using generalized linear models with a log link, the Poisson family and robust standard errors, we estimated risk ratios and 95 % confidence intervals across seafood intake categories.

The Omega study, a study of risk factors for pregnancy complications among women recruited from prenatal clinics in Washington State, USA, 1996–2008.

The current study included 3279 participants from the Omega study.

Median (interquartile range) shellfish, lean fish and fatty fish intake was 0·3 (0–0·9), 0·5 (0–1·0) and 0·5 (0·1–1·0) servings/week, respectively. Lean fish intake of >1 servings/week (v. <0·2 servings/month) was associated with a 1·55-fold higher risk of preterm birth (95 % CI 1·04, 2·30) and was not associated with the other pregnancy complications. Higher intake of seafood (total or other subtypes) was not associated with pregnancy complications (separately or combined).

Higher intake of lean fish, but not fatty fish or shellfish, was associated with a higher risk of preterm birth; these findings may have significance for preterm birth prevention. Studies of mechanisms and potential contributing factors (including seafood preparation and nutrient/contaminant content) are warranted.