(p=0.1) compared to the Danish subjects, but these differences were not significant. After making allowance for seven potential confounders, an increase in duration of gestation of 5.7 days was found for each 20 percent increase in the ratio of erythrocyte EPA and DHA to AA in the Danish women (95% CI 1.4-10.1 days; p=0.02), but not in Faroese women (95% CI −2.0 to 3.3; p=0.6).
Increased gestational duration has also been investigated using observational studies of women who consumed seafood in geographical locations where there was higher exposure to environmental contaminants. Grandjean et al. (2001) examined a birth cohort from the Faroe Islands whose mothers consumed the meat and blubber from pilot whales in addition to regional fish. In a questionnaire, the women reported that they consumed, on average, 72 g of fish, 12 g of whale meat, and 7 g of whale blubber per day (Grandjean et al., 2001). The estimated intake of polychlorinated biphenyls (PCBs) for these women was 30 µg/g of blubber, and of mercury was 2 µg/g of whale meat (Grandjean et al., 2001). In addition to the increase in contaminant concentrations, there was an approximate 10-fold molar excess of selenium over mercury in serum samples from the subjects. The concentration of EPA in the cord1 serum from the infants of Faroese subjects was strongly associated with a maternal diet rich in marine fats. Gestational length showed a strong positive association with cord serum DHA concentration. Each 1 percent increase in the relative DHA concentration in cord serum phospholipids was associated with an increased duration of 1.5 days (95% CI 0.70-2.22), supporting the hypothesis that increased seafood intake may prolong gestation.
Lucas et al. (2004) concluded from an observational study that infants of the Inuit in Nunavik, Canada, had 2.2-fold higher omega-3 fatty acid (p<0.0001), 18.6-fold higher mercury (p<0.0001), 2.4-fold higher lead (presumably related to maternal smoking as ~85 percent of pregnant Inuit women studied smoked) (p<0.0001), and 3.6-fold higher PCB congener 153 cord blood levels (p<0.0001) compared to levels from infants in southern Québec. Despite the association of seafood intake with environmental contaminants, however, the Nunavik women whose infants were in the third compared to the first tertile of percentage of omega-3 fatty acid out of total highly unsaturated fatty acid (HUFA) cord blood values still had a mean 5.4-day longer gestation duration (95% CI 0.7-10.1; p<0.05). This study also showed a nonsignificant increase in mean adjusted birth weight in the third, compared to the first, tertile among Inuit (difference = 77 g, 95% CI −64 to 217).