• Diet RB
• fetal
• nutrition
• pollution
• pregnancy

Omega-3 fatty acids and other nutrients in fish (used herein to refer to finfish or shellfish) are believed to protect against cardiovascular diseases in adults and also to be beneficial in fetal development.1 2 However, there is a concern that benefits may be offset by the presence of contaminants such as methylmercury (MeHg) and persistent organic pollutants (POPs, including chemicals such as polychlorinated biphenyls, dioxins, various organochlorine pesticides and polybrominated diphenylether, among others).

Despite biological plausibility that POPs are harmful,3–5 inconsistent epidemiological findings on POPs has led experts to conclude that evidence on harmfulness of these contaminants in humans is insufficient to act on.6 7 The level of exposure to these chemicals in fish has been regarded as not high enough to trade off the benefits of fish consumption.8 9 Advisories recommend limited consumption of large fish in pregnant women, mainly focusing on prevention of harmful effects of MeHg on neurodevelopment.

In most randomised controlled trials, the beneficial effects of omega-3 fatty acids on fetal growth are reported.10 11 However, evidence from observational epidemiological studies on the association of fish consumption with fetal growth is conflicting. Mendez et al12 observed that high maternal intakes of crustaceans and canned tuna, not fatty fish, were associated with increased risk of small for gestational age (SGA) births in a cohort from the Mediterranean coast of Spain, thus contributing to the argument “against fish consumption” in pregnant women (see page 216). However, another recent study performed in the same country reported decreased risk of SGA with higher consumption of canned tuna, but increased risk with higher consumption of fatty fish.13 This kind of inconsistency is commonly observed in epidemiological studies on weak or modest risk or preventive factors14 and the final conclusion would be “insufficient evidence …