DHA for Fertility: Does Omega-3 Help You Conceive?

DHA is the omega-3 fat many prenatals add, mostly for pregnancy itself. Whether it helps you get pregnant is a separate question with a much thinner answer. Here is what the studies show, how strong each finding is, and how to get enough.

What is DHA?

DHA (docosahexaenoic acid) is a long-chain omega-3 fatty acid. You get it mainly from oily fish and seafood, or from supplements made from fish oil or algae. EPA is its sister omega-3, and the two often come together in fish oil.

Supplements containing DHA are not FDA-approved. By law, the FDA does not approve dietary supplements or their labels before they are sold.⁸

DHA and fertility: the evidence at a glance

Does DHA help you get pregnant?

The best direct evidence is one prospective study. In the Time to Conceive cohort, 900 women aged 30 to 44, trying for less than three months and with no history of infertility, recorded supplements daily for 2,510 cycles.¹ After adjusting for age, obesity, race, previous pregnancy and other vitamins, cycles with omega-3 supplement use had 1.51 times the probability of conception (95% CI 1.12 to 2.04).¹

The authors flag the limits: it was not a randomized trial, omega-3 users were younger, thinner and more likely to take other vitamins, and the doses were not recorded.¹ A related analysis of blood samples from 200 women in the same cohort found no strong association between serum omega-3 or omega-6 levels and the chance of conceiving.²

A 2018 Harvard review of diet and fertility concluded that long-chain omega-3 fats appear to improve female fertility, while noting that contaminants in shared food sources such as fish may dampen the benefit.⁶ Cochrane’s review of antioxidants and related supplements for subfertile women, which includes omega-3 trials, rated the evidence low to very low quality.⁹

Our grade: possibly helpful, low certainty, and safe to include as part of normal pregnancy preparation.

Why DHA matters once you are pregnant

This is where the evidence is strong. A 2018 Cochrane review of 70 randomized trials with 19,927 women found that omega-3 supplements or foods in pregnancy reduced preterm birth before 37 weeks (13.4% vs 11.9%; RR 0.89) and early preterm birth before 34 weeks (4.6% vs 2.7%; RR 0.58), both with high-quality evidence.³ Low birthweight was also less common.³ There are trade-offs to know about: pregnancies lasting beyond 42 weeks were probably more frequent with omega-3 (2.6% vs 1.6%), and there may be a small increase in babies who are large for gestational age, both with moderate-quality evidence.³ The review found too little evidence to judge most effects on the mother.³

An international expert consensus recommends that pregnant and breastfeeding women aim for an average of at least 200 mg of DHA a day.⁴ Starting before conception means you reach that level from the first weeks.

How to get enough DHA

From fish. FDA and EPA advise people who are or might become pregnant to eat 2 to 3 servings a week (4 ounces each) from their Best Choices list, or one serving from the Good Choices list.⁵ Best Choices include salmon, shrimp, canned light tuna, cod and sardines.⁵

Avoid high-mercury fish. FDA and EPA list king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish and bigeye tuna as choices to avoid.⁵ ASRM notes that elevated blood mercury from heavy seafood consumption has been associated with infertility.⁷

From supplements. If you eat little fish, a prenatal with DHA or a separate DHA softgel can cover the 200 mg target. Algae-based DHA suits vegetarians and vegans.

Should you take a DHA supplement before pregnancy?

If you rarely eat fish, yes, it is a sensible part of preparing for pregnancy, mainly for the pregnancy benefits. Do not expect it to fix fertility problems; the conception evidence is too weak for that. If you eat two or three servings of low-mercury fish a week, you may not need extra.

Check the DHA dose in milligrams on any prenatal you consider. The full nutrient table is in prenatal nutrient doses, and food choices are covered in our fertility diet guide. Choline is another nutrient that many prenatals leave out: see choline before pregnancy. More in the Prepare hub.