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.

Birthweight

Evidence from Epidemiologic Studies

A cross-national comparison of infant birthweight for the period 1969–1981 found that Faroe islanders had the highest average birthweight (3610 g) among the 33 countries studied.^[35] Olsen and colleagues hypothesized that this difference (5–9% after standardization) might be attributable to the high fish consumption of the Faroe islanders. Additionally, an observational cohort study from Iceland noted that women who consumed cod liver oil in early pregnancy (~14% of the study population) gave birth to heavier babies than women who did not.^[48] However, other epidemiologic investigations in this area have yielded conflicting results. For example, a large Danish birth cohort study found increased risk for low birthweight (< 10th percentile for estimated gestational age) among infants born to women who consumed more than 60 g of fish per day.^[49] Further analysis found this risk to be confined to consumers of fatty fish and not lean fish. Likewise, in a small Massachussetts cohort, PUFA intake in the highest quartile was associated with a 94 g decrease in birthweight compared with the lowest quartile.^[41] These studies left unanswered the question of whether the observed decrease in growth is attributable to the omega-3 fatty acids or to industrial contaminants found in some fish and seafood.

Evidence from Clinical Trials

By contrast, randomized clinical trials of the use of omega-3 fatty acid dietary supplements during pregnancy have demonstrated no effect on birthweight. In Makrides' Cochrane review of marine oil supplementation during pregnancy,^[45] five trials, including 2302 women, were combined to assess the outcome of low birthweight (< 2500 g). No difference in low birthweights was noted nor was any difference in mean birthweight or small for gestational age found. Likewise, in two recently published systematic reviews of LC-PUFA supplementation among both high- and low-risk women, Horvath and Szajewska^[46,47] found no harmful or beneficial effects on birthweight, low birthweight or recurrent intrauterine growth restriction.

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Cite this: Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing - Medscape - Jan 01, 2010.

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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