Omega-3 Fatty Acids
Omega-3 fatty acids are critical for a healthy pregnancy, especially for the baby’s brain and eyes. Research is inconsistent, however, regarding other possible benefits during pregnancy and whether routine supplementation is necessary.
Health organizations vary widely in their omega-3 recommendations during pregnancy, mostly due to the lack of consistent evidence regarding positive outcomes, which types of omega-3 fatty acids are of benefit, at what dosage, and what is the best ratio of these fatty acids to supplement.
Further, if women adjust their diet to obtain more of these healthy fats through food rather than supplements, pregnant women can benefit from, and consume many other valuable nutrients as well.
However, taking supplements has shown little risk/harm to the mother or fetus and omega-3s (i.e. DHA) are routinely added to prenatal formulations.
Pregnant women who are concerned about their omega-3 intake should talk to their health care provider (HCP). As a general rule, women should never take supplements without first speaking to their HCP.
Background
Omega-3 fatty acids are essential fats (polyunsaturated) that are important components of the membranes that surround each cell in the body. They have roles in oxygen transport, energy storage, and various functions of the heart, blood vessels, lungs, immune system, and hormones.
Although some of these benefits remain debated, these fats may help lower blood pressure and heart rate, improve blood vessel function, and possibly ease inflammation and lower triglycerides.
Docosahexaenoic acid (DHA), a type of omega-3 fatty acid, is a major structural fat in the human brain and eyes, representing about 97% of all omega-3 fats in the brain and 93% of all omega-3 fats in the retina.
There are three types of omega-3 fats. The other two are alpha-linolenic acid (ALA), and eicosapentaenoic acid (EPA). ALA is the most common omega-3 fatty acid in most Western diets.
Pregnancy
A wealth of evidence indicates that pregnant women need omega-3 fatty acids (DHA, specifically) during pregnancy. Debate lies within whether supplementation is required or if this extra need can be met through food. It is possible if women aim specifically for foods with high omega-3 fatty acids, they could obtain significantly more nutritional benefit than if they took supplements alone.
Regardless, omega-3 (EPA and DHA) supplementation during pregnancy is associated with numerous benefits for both mother and infant as the placenta transfers DHA from the mother to the fetus. Note: Breast milk and most commercial infant formulas contain DHA.
DHA may have a role in neural development as the mother’s DHA levels have been observed to be significantly increased right before neural tube closure.
Omega-3 fatty acids are essential in the third trimester of pregnancy when brain growth is at its peak; the fetus rapidly accrues about 50 to 70 milligrams (mg)/day of DHA during this time.
A systematic review published in August 2021 found that while limited, evidence suggests that omega-3 fatty acids during pregnancy may result in favorable cognitive development (knowledge and comprehension) in the fetus/child.
Omega-3 supplements may also slightly increase a baby’s birth weight and the length of gestation (by a few days), reduce miscarriages and growth restriction rates, influence proper brain, retina, and immune system development, and may lower the risk of depression in the mother during and after pregnancy.
Animal studies have shown that both pre-treatment and treatment with DHA may reduce the degree of neonatal adverse affects after a hypoxic ischemic brain injury (when the brain is deprived of oxygen). These brain injuries complicate 2 to 9 out of 1,000 deliveries and may be responsible for up to 14% of all cases of cerebral palsy.
In obese pregnant women, omega-3 fatty acids may also have the potential to reduce placental inflammation (that occurs as a result of obesity).
It is important to note that not all studies have found these same benefits, and it is possible that very high amounts of omega-3 fatty acids need to be consumed to achieve certain positive effects.
Deficiency
There is very little information regarding a lack of omega-3 fatty acids during pregnancy, but deficiency is considered very rare in the United States.
Animal studies have demonstrated that a lack of omega-3 fatty acids may negatively impact brain development in the newborn/infant that may be irreversible in the postpartum period, even with neonatal/infant supplementation.
A general deficiency of omega-3 fatty acids can cause rough, dry skin and dermatitis in adults, as well as decreased growth in infants and children; however, actual cut-off values have not been established for omega-3, or at which point deficiency symptoms are likely to present.
Supplementation
Conflicting results make it difficult to determine which types of omega-3 fatty acids are of benefit (ALA, EPA, or DHA), at what dosage, the true benefits to mothers, infants, or children, whether ALA should be added, and the best ratio of these fatty acids to supplement.
Ratio is important, because only about 4% to 11% of DHA is retro-converted to EPA. Pregnant women who take just DHA supplements without EPA may be unable to produce the right balance which would limit the ability of the fetus to use DHA.
Several reviews have indicated that no recommendation should be made to encourage pregnant women to take omega-3 supplements, especially since most benefits mentioned above are still investigational or have no overall meaningful benefit.
However, numerous organizations have provided guidelines on omega-3 intake during pregnancy:
A wide daily intake range of 200 mg to 1.4 grams (g) per day (1,000 mg equals 1 g) of EPA and DHA (combined) has been recommended by different international organizations and researchers – some of these guidelines advise additional seafood intake, while others endorse supplements, depending on the range recommended.
A study published in April 2021 concluded that health care providers could consider prescribing 1,000 mg DHA daily during pregnancy to reduce early preterm birth in women with low DHA status (as they benefited most from the higher dose, vs. standard 200 mg).
The U.S. National Institutes of Health and the American Heart Association recommend consuming no more than 3 g/day of EPA and DHA combined because these doses could cause bleeding problems (especially with anticoagulant medications) and possibly affect immune function.
Although the inclusion of omega-3 fatty acids in prenatal vitamins is not standard, most prenatal vitamins in the United States contain 200 to 300 mg of DHA/EPA.
Women in the United States are estimated to consume approximately 89 to 100 mg/day of omega-3 fatty acids without supplementation or additional fish intake.
Supplemental sources of DHA include fish oil capsules, krill oil, and algal oil (vegan), which provide variable amounts of DHA and are low in contaminants such as mercury; cod liver oil should be avoided because it is high in vitamin A.
Most commercially available fish oil supplements contain less than 1 to 2 ppb of mercury; the risk of mercury toxicity is considered inconsequential.
Algae used for supplements are grown in tanks and never come in contact with the ocean.
Side effects from taking omega-3 supplements in smaller amounts are usually mild, but may include an unpleasant taste in the mouth, bad breath, heartburn, nausea, stomach discomfort, diarrhea, headache, and smelly sweat.
Not all oil supplements contain EPA so it is important to check the label. Although research is lacking on the effects of DHA alone versus DHA and EPA, some studies have shown the combination may be better than DHA alone.
Food Sources
Oily fish (salmon, sardines, herring, catfish, halibut, and canned tuna) are particularly high in omega-3, along with crab, lobster, mahi mahi, shrimp, and mackerel.
It is estimated the recommended amount of 2 to 3 servings of fish per week is only enough DHA/EPA to meet the lower range recommendations and that supplements is likely required. Other sources disagree, and indicate that depending on the type of fish, eating 8 to 12 oz of seafood per week could be equivalent to as much as 900 mg EPA/DHA per day (read Seafood for more information).
Nuts (especially walnuts), flax seeds, leafy vegetables are rich in omega-3 fatty acids.
Certain vegetable oils like flaxseed, canola, and soybean are also good sources. One teaspoon of corn oil can satisfy the daily omega-6 requirement, but most individuals eat 10 to 20 times this amount.
Some foods are also fortified with DHA, such as certain brands of eggs, yogurt, juices, milk, soy and certain beverages.
Action
While research remains inconsistent regarding whether all women should take DHA/EPA supplementation during pregnancy, these supplements are not associated with fetal harm and likely offer numerous benefits for fetal growth and development, when taken appropriately.
Pregnant women who are concerned about their omega-3 intake during pregnancy should talk to their HCP. HCPs can provide an assessment of a woman's overall diet during pregnancy and determine whether a woman may be at risk for certain nutritional deficiencies or may require supplementation or diet changes. Women should never take supplements without speaking to their HCP first.
Resources
Omega-3 Fatty Acids Fact Sheet (U.S. National Institutes of Health)