DHA is one of the most important nutrients for pregnancy because it directly builds your baby’s brain and eyes. It’s an omega-3 fatty acid that serves as a structural building block of cell membranes in the central nervous system, and your baby needs a large supply of it, especially during the final months of pregnancy. Beyond fetal development, DHA also lowers the risk of preterm birth and may protect against postpartum depression.
How DHA Builds Your Baby’s Brain
DHA is a structural component of the membranes that surround every neuron in the brain. It supports neuronal cell growth and differentiation, meaning it helps new brain cells form and specialize into the types needed for different functions. Beyond that structural role, DHA acts as a precursor to signaling molecules that help neurons communicate with each other, and it activates gene transcription factors that regulate how the brain develops at a cellular level.
The third trimester is when this matters most. DHA accumulates rapidly in fetal brain tissue during the last three months of pregnancy, which is when the brain undergoes its fastest growth. This timing means your DHA intake in the second half of pregnancy has an outsized effect on your baby’s neurological development.
Effects on Vision
The retina, like the brain, incorporates a large amount of DHA during the third trimester. Higher DHA levels in both maternal and infant blood are directly correlated with better visual development in newborns. In a randomized trial, pregnant women who took 400 mg of DHA daily from 16 weeks until delivery had infants with measurably better visual acuity at 60 days of age compared to those who received a placebo. A larger study using 600 mg per day found improved visual acuity particularly in male newborns.
The connection between DHA and vision extends beyond the newborn period. Infants who were breastfed by mothers with low DHA in their milk (below 0.17% of total fatty acids, compared to an optimal range of 0.3 to 0.4%) showed reduced visual acuity and delayed language development compared to those receiving higher-DHA breast milk.
Reduced Risk of Preterm Birth
This is one of the most clinically significant benefits. A multicenter randomized controlled trial found that DHA supplementation reduced preterm birth rates by 62% among women with threatened preterm labor. Across a broader analysis of nine randomized trials involving over 5,200 participants, DHA supplementation lowered the risk of very early preterm birth (before 34 weeks) from 4.6% to 2.7%, a 42% relative reduction. This evidence is strong enough that major health organizations now cite preterm birth prevention as a primary reason for recommending DHA during pregnancy.
Postpartum Depression and Maternal Mood
Pregnancy depletes your DHA stores because your body prioritizes transferring it to the baby. Women who develop postpartum depression tend to have lower blood levels of DHA after delivery compared to those who don’t. Cross-national data shows that populations with higher fish consumption, and consequently higher DHA concentrations in breast milk, have lower rates of postpartum depression overall.
The relationship isn’t perfectly consistent across every study, and some research has not found the same link. But the pattern of DHA depletion during pregnancy, combined with the association between low DHA and depressive symptoms, suggests that maintaining adequate intake may offer some protective benefit for maternal mental health.
Longer-Term Cognitive Benefits for Children
The evidence for lasting IQ or attention benefits is more nuanced. In the KUDOS trial, one of the larger studies tracking children over time, mothers whose DHA blood levels actually increased during the study (indicating they took their supplements consistently) had children who scored higher on verbal and full-scale IQ tests at ages 5 and 6. However, those differences were no longer statistically significant after accounting for socioeconomic factors, which makes it difficult to separate the DHA effect from other advantages in a child’s environment.
What’s clearer is the impact during infancy. DHA supplementation during pregnancy consistently improves visual attention in the first year of life. The long-term cognitive picture likely depends on many factors, but ensuring adequate DHA during pregnancy gives the developing brain the raw materials it needs during its most rapid growth phase.
How Much DHA You Need
Most major health organizations converge on similar numbers. The baseline recommendation for all women of childbearing age is at least 250 mg per day of combined DHA and EPA (the two main omega-3s). During pregnancy, you need an additional 100 to 200 mg of DHA specifically, bringing the practical target to roughly 350 to 450 mg of combined omega-3s daily, with at least 200 mg coming from DHA.
If your diet is low in DHA (below about 150 mg per day) or if blood testing shows low levels, the recommendation increases significantly: 600 to 1,000 mg per day of DHA alone or combined with EPA. This higher dose is the range that showed meaningful reductions in preterm birth in clinical trials. Ideally, supplementation at this level should begin by 20 weeks of pregnancy and continue until around 37 weeks or delivery.
Best Food Sources
Fatty fish is the richest dietary source of DHA. Salmon and herring are among the best options because they’re high in omega-3s and low in mercury. Canned skipjack (light) tuna is also classified as a “best choice” by the FDA for mercury safety. The FDA recommends pregnant women eat two to three servings per week of fish from their “best choice” category, or one serving from the “good choice” list.
The fish to avoid during pregnancy are the large, long-lived predatory species that accumulate mercury: shark, swordfish, king mackerel, tilefish, and orange roughy. Mercury can cause brain damage and developmental delays in a growing fetus, so steering clear of these is important regardless of their omega-3 content.
Choosing a Supplement
If you don’t eat fish regularly, a supplement is a practical way to reach your target. The two main options are fish oil and algal oil. Fish oil tends to contain more EPA than DHA, while algal oil (derived from algae) is naturally high in DHA and low in EPA. This makes algal oil a particularly efficient choice if your goal is specifically to boost DHA, and it’s the only option for those following a vegetarian or vegan diet.
In a study comparing different DHA sources in breastfeeding mothers, algal oil supplementation produced the highest increase in infant blood DHA levels compared to fish oil or DHA-enriched eggs. Fish oil up to 3 grams daily is classified as “generally recognized as safe” by the FDA. Both forms are effective at raising DHA levels in breast milk and maintaining them through lactation, whereas unsupplemented mothers see a natural decline in breast milk DHA as lactation progresses.