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Moderate evidenceWomen's health

Prenatal DHA

Omega-3 in pregnancy has a genuine effect on prolonging gestation, which is better supported than the brain-development claim it is usually sold on. Cognitive benefits for the child have not held up in trials.

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What the science says

  • Reduced preterm birth Moderate evidence

    A Cochrane review of 70 randomized trials in nearly 20,000 women found that omega-3 supplementation reduced preterm birth before 37 weeks and, more markedly, before 34 weeks. Later large trials have been less positive, which is why this is not graded higher.

  • Benefit may depend on baseline omega-3 status Limited evidence

    An exploratory analysis of a large randomized trial found the reduction in early preterm birth was concentrated in women who started with low omega-3 levels. This is a secondary, hypothesis-generating finding.

  • Child cognitive development Limited evidence

    The same Cochrane review found little or no difference in child cognitive and visual outcomes with prenatal omega-3. The brain-development marketing claim is not supported by the trial evidence.

Dosage & safety

Studied doseTrials generally used 500-1000 mg of combined DHA and EPA daily, with at least 500 mg DHA, from around mid-pregnancy. Most prenatal DHA products supply 200-300 mg DHA, below the trial doses.
SafetyWell tolerated; fishy aftertaste and reflux are the usual complaints. Very high doses may prolong bleeding time, which matters around delivery and with anticoagulants. Choose products tested for mercury and other contaminants; avoid cod liver oil in pregnancy because of its vitamin A content.

How to take it

TimingTiming does not matter; from around mid-pregnancy in the trials.
With food?With a meal containing fat, which improves absorption and reduces reflux.
Worth knowingKeeping the capsules in the freezer largely eliminates the fishy repeat, and avoid cod liver oil in pregnancy because of its vitamin A.

Interactions

With medications

  • warfarin, DOACs and antiplatelet drugs

    High-dose omega-3 can prolong bleeding time. tell your obstetrician and anticoagulation team before starting

With other supplements

  • other fish oil, krill or algal oil products

    Easy to stack well past the intended dose without noticing. count the total DHA and EPA across everything you take

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does taking DHA in pregnancy prevent preterm birth?

Omega-3 in pregnancy does reduce preterm birth: a Cochrane review of 70 trials in nearly 20,000 women found fewer births before 37 weeks and especially before 34 weeks. Later large trials were less positive, so the grade is moderate.

Does prenatal DHA boost baby brain development?

No: the same Cochrane review found little or no difference in children's cognitive and visual outcomes with prenatal omega-3. The brain-development claim prenatal DHA is sold on is not supported.

How much DHA should I take while pregnant?

Trials generally used 500-1000 mg of combined DHA and EPA daily, with at least 500 mg DHA, from around mid-pregnancy. Most prenatal DHA products supply only 200-300 mg DHA, below the trial doses.

Is prenatal DHA safe?

Prenatal DHA is well tolerated, with fishy aftertaste and reflux the usual complaints. Very high doses may prolong bleeding time, which matters around delivery and with anticoagulants, and cod liver oil should be avoided in pregnancy because of its vitamin A.

Scientific references

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