Most experts recommend at least 200 mg of DHA per day during pregnancy, on top of a baseline of 250 mg per day of combined DHA and EPA (the two main omega-3 fatty acids). In practical terms, that means pregnant women should aim for roughly 300 to 450 mg of total omega-3s daily, with DHA making up at least two-thirds of that amount. The World Health Organization sets its recommendation at 300 mg per day of combined DHA and EPA, with at least 200 mg coming specifically from DHA.
Why DHA Matters During Pregnancy
DHA is the dominant omega-3 fatty acid in brain gray matter, making up about 15% of all fatty acids in the frontal cortex. It plays a direct role in how neurons form, how synapses develop, and how signals travel between brain cells. It’s also a key structural component of the retina, meaning it influences both cognitive function and eyesight development in the baby.
The fetal brain accumulates DHA throughout pregnancy, but the rate accelerates dramatically in the third trimester. Between weeks 29 and 40, the baby’s brain is pulling in DHA at its highest pace. In fact, DHA accumulation during the last five weeks of pregnancy is roughly double what occurs in the first 35 weeks combined. During the final trimester, the fetus takes in about 50 to 70 mg of DHA per day from the mother’s supply.
Preterm Birth Risk Reduction
The clearest clinical benefit of DHA supplementation during pregnancy is a lower risk of preterm birth. Across 26 randomized controlled trials involving more than 10,000 women, DHA supplementation reduced the rate of birth before 37 weeks from 13.4% to 11.9%. The effect was even more pronounced for very early preterm birth (before 34 weeks), where rates dropped from 4.6% to 2.7%, nearly cutting the risk in half.
One important caveat: starting DHA supplements after a diagnosis of threatened preterm labor does not appear to reduce preterm birth rates. The protective benefit comes from consistent intake before complications arise, which is why guidelines recommend starting early.
When To Start Taking DHA
The most rapid brain and retinal development happens in the second half of pregnancy, particularly the third trimester, which is why DHA was long thought to matter most late in pregnancy. But current guidance is to begin at the onset of pregnancy, or even before. Women who are planning to become pregnant benefit from building up their DHA stores in advance, so there’s an adequate supply once fetal demand spikes.
DHA intake should continue through the end of pregnancy and into breastfeeding. The baby’s brain continues to require DHA for neuron formation and synapse development during the first two years of life, and breast milk is the primary delivery route for nursing mothers.
How DHA Connects to Postpartum Depression
Pregnancy depletes a mother’s DHA reserves. The fetus draws heavily from maternal stores, and if those stores aren’t replenished, blood levels of DHA can drop significantly by delivery. Clinical and population-level studies consistently link low DHA levels to a higher risk of postpartum depression. Women who later developed postpartum depression tended to have lower blood DHA levels after delivery compared to those who didn’t.
Cross-national data reinforces this pattern: countries with higher fish consumption, reflected in higher DHA concentrations in breast milk, have lower rates of postpartum depression. Women with more than one child or with less than 24 months between pregnancies face higher risk, consistent with the idea that repeated pregnancies can drain omega-3 stores faster than the body replenishes them. Maintaining adequate DHA intake throughout pregnancy and postpartum helps protect against this depletion.
Best Food Sources of DHA
Fatty fish is the richest dietary source of DHA, and several varieties are both high in omega-3s and low in mercury. The omega-3 content below (combined DHA and EPA) is per 3-ounce cooked serving:
- Farmed Atlantic salmon: 1.83 grams
- Atlantic herring: 1.71 grams
- Wild Atlantic salmon: 1.57 grams
- Whitefish: 1.38 grams
- European anchovies: 1.23 grams
- Atlantic mackerel: 1.02 grams
- Canned pink salmon: 0.91 grams
- Wild rainbow trout: 0.84 grams
- Canned sardines: 0.83 grams
All of these are classified as “best choice” for mercury by the FDA, meaning they’re safe to eat two to three times per week during pregnancy. A single 3-ounce serving of salmon provides well over the daily DHA target, so even two servings per week can cover most of your needs. Canned skipjack tuna is also a low-mercury option, though its omega-3 content is considerably lower.
Supplements: Fish Oil vs. Algal Oil
If you don’t eat fish regularly, a DHA supplement can fill the gap. The two main options are fish oil and algal oil (derived from microalgae, which is where fish get their DHA in the first place). Algal oil is the go-to for vegetarians and vegans, but it works equally well for anyone.
A randomized, double-blind clinical trial comparing the two found that DHA from algal oil is absorbed into the bloodstream at a rate statistically equivalent to fish oil. After both 6 and 14 weeks of use, plasma DHA levels were non-inferior between the groups. So the choice between them comes down to preference, dietary restrictions, and tolerance. Some women find algal oil easier on the stomach, while others prefer fish oil capsules that combine DHA and EPA.
When choosing a supplement, look for one that provides at least 200 mg of DHA per capsule. Many prenatal vitamins include some DHA, but the amount varies widely, so check the label. Some contain only 50 to 100 mg, which may need to be topped up with an additional supplement.
Upper Limits and Safety
The European Food Safety Authority has established a safe level of intake of 1 gram (1,000 mg) per day for supplemental DHA alone. This applies to all populations, including pregnant and lactating women. There is no formally established upper limit beyond that because the long-term data on doses above 1 gram per day are insufficient to rule out bleeding risks.
At very high doses (well above typical supplement ranges), omega-3 fatty acids can increase bleeding time and reduce platelet clumping. These effects have been observed in studies using up to 9 grams per day, far above what any pregnancy guideline recommends. At the recommended 200 to 300 mg range, side effects are minimal and typically limited to mild digestive discomfort or a fishy aftertaste.
Checking Your Omega-3 Levels
Some practitioners now use a blood test called the Omega-3 Index, which measures the percentage of EPA and DHA in red blood cell membranes. For pregnancy, the suggested target range is 8% to 11%, with DHA alone ideally between 8% and 9%. Previous guidelines suggesting a DHA level of 5% now appear to be too low based on more recent evidence. If your Omega-3 Index is below 8%, you likely need to increase your fish intake or supplement dose to reach the protective range. This test isn’t routine in most prenatal care, but it’s available through direct-to-consumer lab services and some OB-GYN practices.