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Gene Variant Predicts Which Pregnant Women Benefit From Higher-Dose DHA

On 1,000 mg of DHA a day, carriers of one gene version had fewer early preterm births; non-carriers more often went past 40 weeks.

By Dr. Axe Editorial Team · October 21, 2026 · 1 source · Understand

A secondary analysis of a randomized DHA trial, published October 8, 2026 in PLOS Medicine, found that a common gene variant predicted which pregnant women had fewer early preterm births on a higher daily dose of the omega-3 fat DHA.

761women analyzed

1,000 vs 200mg DHA

Researchers reanalyzed the ADORE trial, in which 1,032 pregnant women at three U.S. medical centers completed 200 or 1,000 milligrams of DHA a day, starting at 12 to 20 weeks of pregnancy. Of these, 761 had genetic testing for the FADS Indel, a variant that raises how much arachidonic acid the body makes. Among carriers of the insertion allele, early preterm birth (before 34 weeks) occurred in 4.3% on the low dose versus 1.1% on the high dose, and preterm birth (before 37 weeks) fell from 14.5% to 9.3%. Women without the insertion allele saw little effect from the higher dose, and on it they were 1.59 times as likely as carriers to give birth beyond 40 weeks. Black women carried the insertion allele far more often (85.3% versus 47.3%). Adverse events tracked in the trial included death, life-threatening events, hospital admission, incapacity and birth defects related to DHA intake; this analysis does not report their rates.

Arachidonic acid feeds the prostaglandins that help start labor, and DHA blocks that pathway, so carriers may need more DHA to offset it. Because the genotype comparison came after the trial, it shows a pattern, not proof that matching doses to genes changes outcomes.

Early Preterm Birth: 200 mg vs 1,000 mg DHA in Gene Variant Carriers

PLOS Medicine, 2026, Li et al.

The genotype comparison was not planned before the trial started, and some groups had very few preterm births; the authors say a trial designed to test genotype-guided dosing is needed.

Dr. Axe’s Take

The same 1,000 milligrams of DHA cut early preterm birth in women with one version of this gene and did little for women without it, whose pregnancies more often ran past 40 weeks. I'd like to see prenatal DHA doses matched to the woman's genes. Genetic testing for this variant isn't routine yet, so for now I'd focus on steady DHA from food, like wild salmon, sardines and pasture-raised eggs, and plan any higher-dose supplement with your prenatal provider.

— Dr. Axe

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Study summary

Who: 761 pregnant women (12–20 weeks), three U.S. medical centers, from the ADORE trial
Design: Post hoc secondary analysis of a randomized, double-blind trial; Bayesian models
Dose: 200 mg/day vs 1,000 mg/day DHA, genotyped for FADS Indel variant
Primary result: Early preterm birth in insertion-allele carriers: 4.3% (200 mg) vs 1.1% (1,000 mg); little effect in D/D women
Secondary: Preterm birth in insertion-allele carriers: 14.5% vs 9.3%; on the high dose, births beyond 40 weeks 1.59 times as frequent in D/D women as in carriers
Funding / conflicts: Funder listed in the journal record: National Institute of Child Health and Human Development. Conflict statement in the PubMed record: The authors have declared that no competing interests exist.
Date: Oct 8, 2026