DHA is an omega-3 fat that makes up much of your baby’s brain and the light-sensing layer of the eye. You get it from fish, or from algae-based supplements if you don’t eat fish. Most pregnant women in the U.S. eat well under the recommended amount of seafood.

The short version

  • How much: the United States has no official daily amount for DHA. Expert groups suggest at least 250 mg a day of DHA plus EPA (a related omega-3), with an extra 100 to 200 mg of DHA during pregnancy. Eating 8 to 12 ounces of lower-mercury seafood a week gets you to about 250 mg, according to the NIH.
  • Most women fall short: in national survey data from 2001 to 2014, pregnant women in the U.S. ate about 3 ounces of seafood a week on average.
  • What DHA may do: DHA supplements lower the risk of preterm birth. Whether they help a baby’s thinking or vision is less clear.
  • Mercury: choose lower-mercury fish and skip 7 high-mercury ones (list below).
  • Prenatal vitamins: many don’t include DHA. Check the label.

What DHA does

DHA (docosahexaenoic acid) is a long-chain omega-3 fat. It’s especially concentrated in the brain and the retina, according to the NIH. DHA builds up fastest in a baby’s brain during the third trimester. The buildup in the retina is complete by birth, and the brain keeps building DHA for about 2 years after.

The omega-3 in plant foods, called ALA (found in walnuts, flaxseed, chia seeds, and canola oil), can turn into DHA in your body, but only a little: less than 15%. So the practical ways to raise your DHA are fish and algae-based products.

What the research shows

  • Eating seafood. A review of 29 studies that followed more than 100,000 mothers and children found that mothers who ate about 4 ounces of seafood a week had children with better thinking and learning development. These studies show a link, not proof, since other habits can differ too.
  • Supplements and a baby’s brain and eyes. Trials of EPA and DHA supplements in pregnancy have not shown consistent benefits for a baby’s thinking or vision.
  • Supplements and preterm birth. This is where the evidence is strongest. A 2018 Cochrane review of 70 trials with nearly 20,000 women found that omega-3 supplements lowered the risk of preterm birth (before 37 weeks) by 11% and early preterm birth (before 34 weeks) by 42%, and lowered the risk of low birth weight. A 2022 statement that added two newer large trials found similar results: 12% and 35%.

How much, and how to get it

The National Academies have set an adequate amount for the plant omega-3 (ALA) in pregnancy, 1.4 grams a day, but none for DHA or EPA. Here is what the main U.S. sources recommend, as summarized by the NIH:

Source What it recommends
ACOG, FDA, and the Dietary Guidelines for Americans 8 to 12 ounces a week of seafood that is lower in mercury
A clinical practice guideline in a maternal-fetal medicine journal At least 250 mg a day of DHA plus EPA from food or supplements, plus 100 to 200 mg more of DHA during pregnancy, to lower the risk of preterm birth
The same guideline, for women with low DHA intake (under 150 mg a day) 600 to 1,000 mg a day of DHA, starting in the second trimester and no later than 20 weeks
Dietary Guidelines, for vegetarian and vegan women Ask your provider whether you need an EPA and DHA supplement

In that same survey data, pregnant women got about 77 mg of DHA a day on average from food and supplements combined, well under those amounts. Providers can estimate your DHA intake with a short 7-question tool, which helps decide whether you need a supplement.

Fish

The FDA says to eat 2 to 3 servings a week from its “Best Choices” list. A serving is 4 ounces. Here is how common choices compare, using NIH values for 3 ounces of cooked fish:

Fish DHA (mg)
Salmon, farmed Atlantic 1,240
Salmon, wild Atlantic 1,220
Herring 940
Sardines, canned in tomato sauce 740
Salmon, pink, canned 630
Mackerel, Atlantic 590
Trout, rainbow 440
Oysters, eastern, cooked 230
Tuna, light, canned in water 170
Shrimp 120
Tilapia 110
Cod 100

All of these are on the FDA’s Best Choices list. For example, one 4-ounce serving of farmed Atlantic salmon has about 1,650 mg of DHA, or about 235 mg a day when spread across a week. Two servings a week works out to about 470 mg a day, which covers the 250 mg plus 100 to 200 mg of DHA the guideline suggests. Shrimp, tilapia, cod, and canned light tuna are low in mercury but also low in DHA.

Fish to skip. The FDA advises pregnant women to avoid 7 fish with the highest mercury levels: king mackerel, marlin, orange roughy, shark, swordfish, bigeye tuna, and tilefish from the Gulf of Mexico. Albacore (white) tuna, halibut, mahi mahi, and snapper are on the “Good Choices” list: the FDA says to limit these to 1 serving a week.

Fish caught by family or friends. Check local fish advisories. If there’s no advisory, eat one serving and no other fish that week, according to the FDA.

Mercury versus benefit. Reviews show that the benefits of eating seafood during pregnancy outweigh the risk from mercury, as long as you choose lower-mercury types, according to the NIH. ACOG advises avoiding raw or undercooked fish and shellfish, so cook oysters and other seafood fully.

If you don’t eat fish

  • Algae-based DHA is a vegetarian source. Algal oil supplements usually have 100 to 300 mg of DHA. In a small study, DHA from algal oil was absorbed as well as DHA from cooked salmon.
  • Fish oil supplements vary. A typical 1,000 mg capsule has about 180 mg of EPA and 120 mg of DHA, so look for the DHA amount on the label. Fish oil supplements haven’t been found to contain mercury, which is removed during processing.
  • Cod liver oil also contains vitamin A. Too much preformed vitamin A in pregnancy can cause birth defects, so ask your provider before using it.
  • Foods with added DHA, such as some eggs, yogurt, juices, milk, and soy drinks, are another option. Check the label.
  • Prenatal vitamins don’t typically include omega-3s, according to the NIH, though some come with a separate DHA capsule. Look for “DHA” in milligrams on the Supplement Facts panel. See Prenatal Vitamin Questions, Answered.

Safety

  • Amounts: the National Academies haven’t set an upper limit for omega-3s. The FDA considers supplements with up to 5 grams a day of EPA and DHA combined safe when used as directed, and says labels shouldn’t recommend more than 2 grams a day, according to the NIH. The amounts discussed for pregnancy are far lower. Doses of 2 grams a day or more may lengthen bleeding time, so don’t go beyond the label or your provider’s advice.
  • Side effects are usually mild: an unpleasant taste, bad breath, heartburn, nausea, stomach upset, diarrhea, headache, or sweat with an odor.
  • Blood thinners: fish oil can interact with warfarin and similar medicines. If you take one, ask your provider before starting a supplement.
  • Quality: choose a product tested by an independent group such as U.S. Pharmacopeia (USP), NSF, or ConsumerLab.
  • While breastfeeding: DHA passes into breast milk, and the FDA’s fish advice applies to breastfeeding women too: 2 to 3 servings a week from the Best Choices list. See Prenatal Vitamins While Breastfeeding.

What to do now

  • Plan 2 servings of lower-mercury fish a week, such as salmon, sardines, herring, or trout, cooked through.
  • Skip the 7 high-mercury fish listed above.
  • Check your prenatal vitamin for DHA, in milligrams. If it has none and you eat little fish, ask your provider whether to add a DHA supplement.
  • If you’re vegetarian or vegan, ask about an algae-based DHA supplement.
  • If you take a blood thinner, ask before starting fish oil.
  • Check with your provider before using cod liver oil.

Related reading

Sources

Updated November 2026. This article is for general information and is not a substitute for advice from your health care provider.