What the ORIP Trial Found
A major New England Journal of Medicine study—ORIP (Omega-3 fats to Reduce the Incidence of Prematurity)—tested whether DHA-rich fish oil could prevent very early preterm birth (before 34 weeks). Among ~5,400 Australian women, DHA did not lower early preterm birth risk overall, particularly in those already getting meaningful DHA from diet or standard prenatal supplements. These headline results sit in tension with a late-2018 Cochrane Review showing omega-3s reduce preterm birth by 11% and early preterm birth by 42%, underscoring that the context—especially baseline omega-3 status—matters.
Why the Results Likely Differed from Earlier Reviews
Elevated Baseline DHA in Participants
In Australia, perinatal supplement use is common. ORIP excluded women taking >150 mg/day DHA, yet still enrolled >700 women regularly consuming ≤150 mg/day. This likely nudged baseline DHA higher than in prior trials. Indeed, baseline blood DHA in ORIP (~4.5% in whole blood; ~RBC-equivalent) was about 20% higher than in KUDOS, a study that did show fewer early preterm births with supplementation.
Shortening the Supplement Window
ORIP began DHA earlier than the DOMInO trial but stopped at 34 weeks to avoid post-term interventions. Many other studies continued to delivery. With 6–8 DHA-free weeks during peak maternal-to-fetal fat transfer, any protective effect could have been blunted.
Including Multiple Gestations
ORIP included twins and higher-order pregnancies, which are naturally shorter. Most trials in the Cochrane review excluded multiples for exactly this reason. In ORIP’s supplemental analyses restricted to singleton pregnancies, a protective signal emerged.
What the Blood Levels Tell Us
Modest Rise Despite High Dose
Kristina Harris Jackson, PhD, RD, noted baseline DHA near 4.5% (whole blood), rising only to ~5.1% at 34 weeks with 900 mg/day DHA, versus ~4.1% in controls. By contrast, 200 mg/day in the third trimester has raised RBC DHA by ~1.1% elsewhere. The small gain in ORIP raises questions about adherence, formulation, timing, or background intake.
Risk Tracks with Starting DHA
Supplemental data showed early preterm birth risk tracked baseline DHA quartiles: higher starting DHA aligned with lower risk. Among supplemented women, those with high baseline levels didn’t clearly benefit further—consistent with a ceiling effect. Conversely, women in the lowest baseline quartile (<~4% RBC DHA) appear most likely to benefit from DHA.
Practical Takeaways for Clinicians and Patients
Personalize, Don’t Generalize
ORIP’s central lesson is not that DHA “doesn’t work,” but that one-size-fits-all dosing is suboptimal. Women who already eat fish or take multivitamins with fish oil may see little additional benefit, whereas those with low omega-3 status are the prime candidates for supplementation.
Test, Target, and Titrate
Measuring DHA early in pregnancy provides a clear starting point. Jackson’s work proposes a protective target of ≥5% DHA (RBC). Women below that threshold can increase fish intake or add DHA (often 200–600 mg/day is sufficient; higher doses may be used for very low baselines), then retest to confirm they’ve reached the zone. This approach underpins the Prenatal DHA Test, a simple dried blood spot assay designed to guide dosing decisions.
Consider Timing and Continuity
Maintaining DHA through delivery may matter for both maternal gestation and fetal accretion, given third-trimester transfer surges. Unless there’s a specific obstetric reason to stop, many protocols continue DHA to birth.
Bottom Line
The ORIP trial reinforces a nuanced truth: DHA’s benefit for preterm birth prevention is most pronounced in women starting with low omega-3 status. A targeted strategy—measure baseline DHA, supplement if low, and verify you’ve reached ≥5%—is more sensible than blanket dosing for everyone.
