Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing

Ellen Mozurkewich; Deborah R Berman; Julie Chilimigras

Expert Rev of Obstet Gynecol. 2010;5(1):125-138.

Advice to Pregnant Women

Although per capita fish consumption in the USA falls in the mid-range on cross-national studies, pregnant women may consume less seafood than the general population because of fear of environmental contaminants.^[25,26] Despite the potential benefits of dietary sources of EPA and DHA, dietary fish consumption exposes pregnant mothers to industrial contaminants, namely methyl mercury and polychlorinated biphenyls. In the late 1960s, following widespread inorganic mercury contamination of the Shiranui Sea in Japan, maternal exposure to very high mercury levels in fish was recognized to be the cause of Minamata disease, resulting in mental retardation in exposed offspring.^[27,28] Subsequent epidemiologic studies of populations, such as Seychelle and Faroe islanders, with high dietary intake of fish from waters with more moderate mercury contamination have yielded mixed results. Some, but not all, studies of children born to mothers with high fish consumption have suggested that lower levels of mercury may be associated with subtle adverse developmental consequences.^[29,30] Prenatal exposures to polychlorinated biphenyls through fish has also been found to be associated with adverse developmental effects.^[31] The DHA and EPA content of dietary fish and shellfish, as well as levels of industrial contaminants, are listed in Table 1.

The risk–benefit analysis of dietary fish consumption during pregnancy is consequently a matter of some controversy. Pregnant women receive conflicting advice regarding the desirability of dietary fish consumption from the US FDA, who advises limiting prenatal fish intake to a maximum of two fish meals per week from species low in mercury, including shrimp, canned light tuna, salmon, pollock and catfish,^[201] and from advocacy groups, such as the Healthy Mothers Healthy Babies Coalition, who recommend greater prenatal fish consumption.^[202] Owing to the uncertain trade-offs of the benefits of fish consumption versus industrial contaminants, some authorities have advised supplementation with highly purified fish oil during pregnancy.^[32] However, some benefits of dietary fish may not be replicated by supplements.^[33] This review aims to identify the best evidence on the benefits and risks of eating fish and the possible role of omega-3 fatty acid supplementation during pregnancy and lactation in maternal and child health and development.

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Table 1. Omega-3 fatty acids and industrial contaminants in commonly eaten fish and shellfish.
Type	EPA + DHA (mg/serving) (oz)	EPA + DHA (mg/100 g) (3.5 oz)	Mercury (µg/g) (ppm)	PCBs (ng/g) (ppb)
Anchovy	1165 (2)	2055	< 0.05
Catfish, farmed	253 (5)	117	< 0.05	< 50
Cod, Atlantic	284 (6.3)	158	0.10
Fish burger (fast food)	337 (2.2)	546	< 0.05	8
Fish sticks, frozen	193 (3.2)	214	< 0.05
Halibut	740 (5.6)	465	0.25
Herring, Atlantic	1712 (3)	2014	< 0.05
Mackerel, Atlantic	1059 (3.1)	1203	0.05
Mackerel, King	618 (5.4)	401	0.73
Mahimahi	221 (5.6)	139	0.15
Pollock, Alaskan	281 (2.1)	468	< 0.05
Salmon, farmed	4504 (6)	2648	< 0.05	15–51
Salmon, wild	1774 (6)	1043	< 0.05	0.5–5
Sardines	556 (2)	982	< 0.05	22–57
Shark	583 (3)	689	0.99
Snapper	546 (6)	321	0.19
Swordfish	868 (3.7)	819	0.98
Trout	581 (2.2)	935	0.07	11
Tuna (light/skipjack)	228 (3)	270	0.12	45
Tuna (white/albacore)	733 (3)	862	0.35	100
Clams	241 (3)	284	< 0.05	2–3
Crab	351 (3)	413	0.09	6
Lobster	71 (3)	84	0.31
Mussels	665 (3)	782	< 0.15	0.8–7
Oysters	585 (3)	688	< 0.05	0.8–17
Scallops	310 (3)	365	< 0.05
Shrimp	267 (3)	315	< 0.05	0.2–2

DHA: Docosahexaenoic acid; EPA: Eicosapentaenoic acid; PCB: Polychlorinated biphenyls; ppb: Parts per billion; ppm: Parts per million.
Adapted from.^[101]

Table 2. Results of clinical trials of omega-3 fatty acid supplementation.
Parameter	Results
Preterm birth:
< 37 weeks	No benefit*
< 34 weeks	Likely benefit^§
Intrauterine growth restriction (small for gestational age)	No benefit
Preeclampsia	No benefit
Perinatal depression:
– Prevention	No benefit
– Treatment	Conflicting results^¶
Neurodevelopmental outcomes:
– Term	Conflicting results
– Preterm	Conflicting results
Prevention of allergic disease	Conflicting results

*The majority of the available clinical trials show no benefit for the intervention.
^§The majority of the available clinical trials show a benefit for the intervention.
^¶Clinical trial results are mixed, with some trials showing benefit and others not.

Box 3. Biologic activities of omega-3 fatty acids.
Decrease proinflammatory cytokine production Precursors of resolvins and neuroprotectins Improve membrane fluidity May counter or promote apoptosis, depending on circumstance Regulate gene expression Act as antioxidants Quicken neurotransmission Modulate intracellular signaling

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