Supplement analysis backed by scientific evidence · PT

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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.

Evidence last reviewed: August 2026

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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.

Scientific references

Where to buy

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