Most pregnant women should aim for 600 to 1,000 mg per day of combined DHA and EPA, the two omega-3 fats that matter most during pregnancy. This is significantly more than the older recommendation of 200 to 250 mg per day, which most populations weren’t even hitting. The higher range is based on clinical trials showing meaningful reductions in preterm birth.
Why the Recommended Dose Increased
For years, health organizations suggested pregnant women get at least 200 mg of DHA daily. That number was based on general nutritional needs. But randomized controlled trials have since tested higher doses and found that 600 to 1,000 mg per day of DHA and EPA (or DHA alone) significantly reduced the risk of both preterm birth and early preterm birth. A 2018 Cochrane review of 70 studies involving nearly 20,000 pregnant women found that omega-3 supplementation cut the rate of early preterm birth (before 34 weeks) nearly in half, dropping it from 4.6% to 2.7%. Babies born to supplemented mothers also had slightly higher birth weights, and fewer of them ended up in neonatal intensive care.
These findings led to updated clinical practice guidelines recommending the higher daily intake of 600 to 1,000 mg. If your prenatal vitamin contains omega-3s, check the label carefully. Many prenatal formulas include only 200 to 300 mg of DHA, which falls short of the dose linked to preterm birth prevention. You may need a separate omega-3 supplement to bridge the gap.
DHA vs. EPA: Which One Matters More
DHA is the omega-3 that gets the most attention during pregnancy because it’s a structural building block of your baby’s brain and eyes. It accumulates rapidly in fetal brain tissue, especially during the third trimester when brain growth accelerates. One study found that infants whose mothers supplemented with 800 mg per day of DHA showed faster visual learning at 4 and 6 months of age compared to infants whose mothers took lower doses. Higher doses appeared to produce greater benefits.
EPA plays a different role. It’s more involved in regulating inflammation and may influence mood. A pilot study found that a combination of EPA and DHA at a ratio of roughly 1.5 to 1 (EPA to DHA) reduced depressive symptoms in women with postpartum depression. While this research is preliminary, it suggests EPA has its own value during the perinatal period. Most fish oil supplements contain both, so you don’t need to choose one over the other. Look for a product that lists the DHA and EPA amounts separately on the label, and prioritize DHA content.
Food Sources That Count
The U.S. Dietary Guidelines recommend that pregnant and breastfeeding women eat 8 to 12 ounces of low-mercury seafood per week. This is enough to provide a meaningful baseline of DHA and EPA, though many women still fall short of the 600 to 1,000 mg target through food alone.
The best low-mercury, high-omega-3 options include salmon, sardines, anchovies, herring, and Atlantic mackerel. Shrimp, pollock, tilapia, and catfish are also safe choices, though they contain less omega-3 per serving. A 4-ounce portion of salmon provides roughly 1,200 to 2,400 mg of combined DHA and EPA, so eating salmon twice a week could meet the target on its own. Sardines and anchovies pack similar concentrations in smaller portions.
Avoid shark, swordfish, king mackerel, tilefish, bigeye tuna, marlin, and orange roughy. These large predatory fish accumulate high levels of mercury, which can harm your baby’s developing brain. If you eat fish caught locally by family or friends, check regional advisories. When no advisory exists, limit locally caught fish to one serving per week and skip other fish that week.
Plant-Based Omega-3s Fall Short
Walnuts, flaxseed, chia seeds, and hemp seeds contain ALA, a plant-based omega-3. Your body can convert ALA into DHA and EPA, but the conversion rate is extremely low, topping out at around 4% for DHA. Even eating large amounts of ALA-rich foods won’t reliably raise your DHA levels enough to meet pregnancy needs.
If you’re vegetarian or vegan, algal oil supplements are the most practical solution. Algal oil is derived from microalgae (the original source of DHA in the marine food chain) and is naturally high in DHA, though typically low in EPA. Studies have shown that algal oil raises infant DHA levels effectively. In one comparison, breastfeeding mothers taking algal oil achieved higher infant DHA levels than those taking fish oil or DHA-enriched eggs. Look for an algal oil supplement that provides at least 600 mg of DHA daily.
Upper Limits and Safety
No formal upper limit has been set for omega-3 intake during pregnancy. The FDA has concluded that combined EPA and DHA supplements up to 5,000 mg (5 grams) per day are safe, and the European Food Safety Authority agrees, noting no evidence of bleeding problems, immune suppression, or blood sugar disruption at that level. That said, the therapeutic range for pregnancy is well below this ceiling. Sticking to 600 to 1,000 mg daily gives you the benefits seen in clinical trials without any reason to worry about excess.
Some older guidance raised concerns that very high doses (above 900 mg EPA plus 600 mg DHA for extended periods) might dampen immune function. At the recommended pregnancy dose, this isn’t a practical concern. Fish oil supplements can cause mild side effects like fishy aftertaste, burping, or mild nausea. Taking them with food or choosing enteric-coated capsules typically helps. Refrigerating your bottle can also reduce the fishy taste.
When to Start Supplementing
Starting omega-3 supplementation early in pregnancy, or even while trying to conceive, gives you the best chance of building adequate DHA levels before your baby’s brain development ramps up. The fetal brain grows throughout pregnancy, but DHA accumulation is heaviest during the third trimester. If you’re already in your second or third trimester and haven’t been supplementing, starting now still provides benefit. The preterm birth prevention trials enrolled women at various gestational ages and still found protective effects.
Your body’s ability to convert plant-based ALA into usable DHA is less than 1% by some estimates, so relying on conversion rather than direct sources means falling behind. Whether through fatty fish, fish oil, or algal oil, getting preformed DHA and EPA into your diet is the only reliable way to reach the levels linked to better outcomes.