Frequency of seafood intake in pregnancy as a determinant of birth weight: evidence for a dose dependent relationship.

STUDY OBJECTIVE: The aim was to explore whether maternal consumption of seafood is a determinant of birth weight in a dose dependent manner. DESIGN: A population based survey of lifestyle factors in pregnancy was linked with information from antenatal and obstetric records. SETTING AND PARTICIPANTS: Seventy five per cent of all 1362 women who delivered in the Faroe Islands during the study period 1986-87 who gave a structured post partum interview on lifestyle factors. MAIN RESULTS: Altogether, 2, 6, 16, 33, 26, 14, and 3% of women had consumed approximately 0, 1, 2, 3, 4, 5, and 6+ respectively seafood (fish or whale) dinner meals per week during pregnancy. The average birth weight (p = 0.02) and birth length (p = 0.002) varied significantly between the seven groups, and increased by about 0.2 kg and 1 cm, respectively between women who ate 0 and those who consumed 3 seafood meals per week. Mean birth weight and length tended to level off with further fish consumption: when fitting a second degree polynomial, the quadratic terms were negative and significant for both birth weight (p = 0.005) and length (p = 0.001). Analogous analyses for pregnancy duration were not significant, but exhibited similar trends. All analyses were adjusted for maternal height, weight, parity, age, marital status, and smoking. CONCLUSIONS: The weight and length of the newborn increased with the frequency of seafood dinner meals consumed in pregnancy but only up to a consumption level of about 3 meals per week.