The available evidence from epidemiologic studies and clinical trials presents a mixed picture regarding the health benefits and potential risks of fish consumption and omega-3 fatty acid supplementation for pregnant women, the fetus and young children. For virtually all of the outcomes we considered where research is available – length of gestation and risk of prematurity, birthweight, hypertension and preeclampsia, depression in pregnancy and postpartum depression, fetal brain development and early childhood IQ, allergy and asthma in children – there is evidence suggestive of benefit for fish intake or omega-3 supplementation; however, there are also many studies showing no benefit, or, in a few instances, possible harmful effects. Evidence from the available randomized, controlled trials is most suggestive of benefit for the outcome of preterm birth before 34 weeks, particularly among women with a prior preterm birth. Results of clinical trials of omega-3 fatty acid supplementation are summarized in Table 2.
In assessing their findings of no impact or negative effect, investigators raised a number of issues, including noncompliance to study protocol requirements on the part of participants,[36] the type of fish products consumed,[49] the possible role of industrial contamination,[41] and the timing of intervention.[56,58,67] It is also worth noting in considering inconsistent findings that data collection methodology varies across studies with use of food frequency questionnaires, surveys, measurement of acid levels and other approaches, making consistent cross-study comparisons difficult. For some outcomes, such as childhood neurodevelopment, the few intervention studies that are available vary in terms of time points used for assessment (i.e., age of children studied), the specific subtests that are considered (e.g., mental processing, intelligence, verbal skills, visual acuity, problem solving, quantitative skills, communication abilities, presocial behavior and attention), and the tools used to evaluate these aspects of behavior. Appropriately powered, randomized, controlled trials are needed that can address these and other issues. Using the highly purified omega-3 fatty acid supplements now available, future trials should benefit from improved participant compliance, which should allow for better determination of true treatment effects. We feel that more investigation is needed to clarify the possible benefits of omega-3 fatty acid supplementation in perinatal depression, early childhood cognitive functioning (including IQ, attention and behavior), and risk for allergic diseases. Current evidence does not support a role for omega-3 fatty acid supplementation for prevention of preeclampsia, pregnancy-induced hypertension, or intrauterine growth restriction. More needs to be learned regarding whether the effects of omega-3 supplements differ between singleton and twin gestation, or between high- and low-risk pregnancies. More research needs to be carried out on the differential effects of eating fish versus taking supplements, and the optimal dosage of omega-3 supplements need to be established.
In the available randomized, controlled trials, doses of omega-3 fatty acids up to 6 g/day have been used. In the USA, the FDA has designated omega-3 fatty acid doses up to 3 g/day as “generally regarded as safe”.[203] In our review of the available studies of fish oil supplementation for high-risk pregnancies, a dose of approximately 1000 mg of DHA appeared to be the most frequently used beneficial dose. Doses of EPA in these studies varied widely between 1300 and 3000 mg, so no optimal dose has been established.[46] Most trials have commenced fatty acid supplementation in the second or third trimester of pregnancy. After reviewing the available evidence, a recent EU-supported Perinatal Lipid Intake Working Group has recommended that all pregnant and lactating women achieve a dietary intake of DHA of at least 200 mg daily. The authors note that DHA intakes of up to 1000 mg/day and total omega-3 LC-PUFA intake up to 2.7 g/day have been used in randomized trials without significant adverse effects.[5]