If you're pregnant and not eating fatty fish once or twice a week, you're far from alone. Fish advice during pregnancy can be confusing, and many women skip fish altogether to avoid mercury. The catch is that fish is also the main dietary source of DHA, the omega-3 your baby uses to build brain and eye tissue. Here's what DHA does, how much fish is safe, how much DHA to aim for, and how to get it if fish isn't on your plate.
Why does DHA matter during pregnancy?
DHA (docosahexaenoic acid) is a long-chain omega-3 fat that is concentrated in the brain and the retina, and it's present in breast milk (NIH Office of Dietary Supplements). A developing baby gets its DHA from you, and international experts note that ALA, the plant omega-3 in flax and chia, is far less effective than preformed DHA at getting DHA into the fetal brain.
Fish itself looks good for babies when mercury is kept low. In a U.S. cohort, each extra weekly serving of fish during pregnancy was linked to higher infant cognition scores, while higher maternal mercury levels were linked to lower scores. The takeaway from that study: keep eating fish, and choose varieties low in mercury.
How much fish is safe to eat while pregnant?
The FDA and EPA's joint advice about eating fish says that during pregnancy and breastfeeding you can eat 2 to 3 servings a week from their "Best Choices" list, or 1 serving a week from the "Good Choices" list. A serving is 4 ounces, roughly the size of your palm.
- Best Choices include salmon, sardines, anchovies, herring, Atlantic mackerel, cod, shrimp and canned light tuna.
- Choices to avoid because of the highest mercury levels: king mackerel, marlin, orange roughy, shark, swordfish, tilefish from the Gulf of Mexico and bigeye tuna.
One thing the charts don't tell you: low mercury doesn't mean high omega-3. Oily fish like salmon, sardines and herring carry far more DHA than lean white fish, so if your weekly servings are mostly cod or fish sticks, your DHA intake may still be low.
How much DHA do you need during pregnancy?
There's no official U.S. intake target for DHA. A consensus of international perinatal experts recommends that pregnant and breastfeeding women average at least 200 mg of DHA a day, which is roughly what one to two portions of oily fish a week provides. The same group noted that trials have used up to 1 g of DHA a day in pregnancy without significant adverse effects.
Check your prenatal vitamin's label: some include DHA and some don't. If yours doesn't, and you aren't eating oily fish most weeks, a DHA supplement is a simple way to close the gap. Talk to your doctor or midwife before adding any supplement during pregnancy, especially if you take blood thinners or have a bleeding disorder.
What does the research say about omega-3s and pregnancy outcomes?
The strongest evidence is for preterm birth. A Cochrane review of 70 randomized trials found that women who took omega-3s had fewer babies born before 37 weeks (11.9% versus 13.4%) and before 34 weeks (2.7% versus 4.6%). Evidence that omega-3s lower the risk of pre-eclampsia was weak, and the review found no clear effect on postpartum depression or on children's later IQ. We go deeper into the research in Omega-3 fatty acids: a pregnancy supplement?
Is flaxseed or algae a good alternative to fish?
Flax, chia and hemp seeds are rich in ALA, but your body converts very little of it: tracer studies estimate about 6% to EPA and 3.8% to DHA, and less on diets high in omega-6 fats. They're healthy foods, but not a reliable DHA source. (Our guide to ALA vs. EPA vs. DHA explains why.)
Algae is a different story. Fish get their omega-3s by eating microalgae, and DHA from algal oil gets into your body just as well: in a randomized study, algal-oil DHA capsules and cooked salmon raised blood DHA levels equally. Algae grown in tanks also sidesteps the mercury question entirely.
That's why we make Head & Heart from algae rather than fish. Each serving provides 500 mg of DHA, and we third-party test every batch for heavy metals and contaminants. If you're plant-based, our guide to getting vegan omega-3 covers food sources too.
