Maternal seafood intake and the risk of small for gestational age newborns: a case–control study in Spanish women

OBJECTIVE: To investigate the relationship between seafood consumption during pregnancy and the risk of delivering a small for gestational age (SGA) newborn. DESIGN: This case–control study included women with SGA newborns and controls matched 1:1 for maternal age (±2 years) and hospital. SETTING: Five hospitals in Eastern Andalusia, Spain. PARTICIPANTS: 518 pairs of pregnant Spanish women. The SGA group included women who delivered SGA newborns: SGA was defined as a birth weight below the 10th percentile of infants at a given gestational age. Controls were women who delivered newborns with adequate birth weights. INTERVENTIONS: We collected data on demographic characteristics, socioeconomic status, toxic habits and diet. Midwives administered a 137-item Food Frequency Questionnaire. OUTCOME MEASURES: We calculated quintiles of seafood intake and applied conditional logistic regression to estimate ORs and 95% CIs. RESULTS: Shellfish intake more than once/week yielded a significant protective effect against an SGA newborn (OR 0.25, 95% CI 0.08 to 0.76, after adjusting for energy, educational level, smoking, prepregnancy body mass index, weight and a history of preterm or low birthweight newborn). The risk of an SGA newborn was lower among women who consumed >29 g/day fish compared with women who consumed ≤8 g (adjusted OR 0.63, 95% CI 0.41 to 0.98; p=0.025 for a trend). Similarly, the risk of an SGA newborn was lower among women who consumed >1 g/day of marine n-3 polyunsaturated fatty acids compared with those who consumed ≤0.4 g/day (adjusted OR 0.58, 95% CI 0.38 to 0.90; p=0.025 for a trend). CONCLUSION: An average seafood intake of at least 29 g/day during pregnancy, equivalent to 2–3 servings/week, reduced the risk of an SGA newborn, compared with an average seafood intake of less than 8 g/day.