Evening Primrose Oil
HerbalAlso called · 4 names▾▴
Evening primrose, EPO, Oenothera biennis, Evening primrose seed oil
Herbal supplement (breast pain and labor induction)
Herbs and supplements are not FDA-approved before sale. About these sources
- Topical
- Other
Research strength: 1 / 5
EMA says evening primrose oil is not recommended during pregnancy because the available human data are insufficient. NCCIH says evidence about use during pregnancy is not conclusive. A 2018 randomized trial and a 2022 review studied use near term, not first-trimester exposure. These sources do not establish first-trimester outcomes for medicinal use. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 1 / 5
EMA says evening primrose oil is not recommended during pregnancy because the available human data are insufficient. NCCIH says evidence about use during pregnancy is not conclusive. A 2018 randomized trial and a 2022 review studied use near term, not second-trimester exposure. These sources do not establish second-trimester outcomes for medicinal use. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 3 / 5
EMA says evening primrose oil is not recommended during pregnancy because the available human data are insufficient. NCCIH reports inconsistent results from attempts to start labor near term. A 2018 randomized trial of 80 low-risk people at 40 weeks found no difference in gestational age, need for induction or augmentation, or labor duration. A 1999 retrospective study of 108 people found no shorter gestation or labor and suggested possible increases in prolonged rupture of membranes, oxytocin use, stalled descent, and vacuum delivery. A 2026 review counted 16 studies with 1,662 participants, but rated 13 at high risk of bias and searched only through March 2023. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- European Union herbal monograph on evening primrose oilEU agencyEuropean guidance
- NCCIH: Evening Primrose OilUS government
- Dove and Johnson, 1999 retrospective studyUS government
- Kalati et al., 2018 randomized clinical trialUS government
- Hutcherson et al., 2022 systematic review of parturitionUS government
- Niazi et al., 2026 systematic review and meta-analysis
Evening Primrose Oil — Breastfeeding
Research strength: 2 / 5
EMA says evening primrose oil is not recommended while breastfeeding because the available human data are insufficient. LactMed describes a small study in which mothers took EPO for eight months and their milk contained more of some fatty acids; the 1991 trial abstract reports milk composition, not infant blood levels or clinical outcomes. NCCIH also says evidence about use during breastfeeding is not conclusive. The available sources do not establish how much EPO reaches an infant or what clinical effects it may have. Ask your provider about your situation.
Last reviewed: 2026-10-16
Pregnancy
Human pregnancy research located concerns term or post-term use, not first- or second-trimester exposure. Kalati et al. (2018) randomized 80 low-risk nulliparous people at 40 weeks to oral EPO 1,000 mg twice daily for seven days or placebo; the abstract reports no significant differences in gestational age at delivery, induction or augmentation, or duration of labor stages. Dove and Johnson (1999) retrospectively compared 54 EPO users with 54 controls; oral use from 37 weeks until birth did not shorten gestation or overall labor, and the authors said it may be associated with prolonged rupture of membranes, oxytocin augmentation, arrest of descent, and vacuum extraction. A 2022 systematic review included 11 studies: seven placebo-controlled randomized trials, one non-placebo randomized trial, one case study, one retrospective study, and one quasi-experimental study; it reported important risks of bias and said further research was needed before use during parturition. A 2023 review included seven trials with 920 women, all at term or post-term, and reported mixed findings across outcomes. A 2026 review reported 16 studies and 1,662 participants, but its search ended in March 2023, it rated 13 studies at high risk of bias, and it lists the 1999 retrospective Dove study as a randomized trial. The 2026 review also has inconsistent descriptions of its study set and pooled outcomes, so its estimates are not treated as settled findings.
Breastfeeding
LactMed describes 36 nursing mothers, two to six months postpartum, assigned to 2 g EPO or placebo twice daily for eight months; it reports increased linoleic acid and gamma-linolenic acid plus a metabolite in milk. The 1991 Cant et al. abstract reports 39 women and states that total milk fat and essential fatty acids rose in the EPO group while declining in the placebo group; it reports milk composition, not infant blood levels or clinical outcomes. The participant totals differ between the LactMed record and the primary abstract. LactMed states that published infant-level information was not found as of its May 2021 revision. EMA says use during lactation is not recommended because data are insufficient. NCCIH describes the evidence as inconclusive.
Evening primrose oil is extracted from Oenothera biennis seeds. NCCIH describes it as containing omega-6 fatty acids, including gamma-linolenic acid. Clinical studies used different oral and vaginal capsule preparations and doses, so findings for one preparation do not establish effects for every product or route.
What was tested
The reviewed human evidence includes small oral pregnancy trials near term, vaginal-use trials near term, one retrospective intrapartum study, systematic reviews, and one small placebo-controlled study measuring breast-milk composition. The pregnancy studies examined labor and cervical outcomes; the 1991 lactation abstract reported milk composition. The breastfeeding primary abstract reported milk composition rather than infant clinical outcomes. The pregnancy sources report no first- or second-trimester studies.
Use during pregnancy
- Source A says
- NCCIH says the evidence about evening primrose oil use during pregnancy is not conclusive and describes inconsistent results in labor-start studies. (NCCIH: Evening Primrose Oil)
- Source B says
- EMA's 2018 herbal monograph says pregnancy use is not recommended in the absence of sufficient data. (European Union herbal monograph on Oenothera biennis or Oenothera lamarckiana oil)
- Why they differ
- NCCIH presents uncertainty about use and labor research, while EMA gives a more precautionary recommendation for its herbal medicinal product when data are insufficient. Neither statement establishes that pregnancy harm has been shown.
- Other sources
- A 2022 systematic review concluded that use for parturition was not recommended and that further research was warranted; it also reported important risks of bias across the studies. (Hutcherson et al., 2022 systematic review of evening primrose preparations for parturition)
- What the evidence shows overall
- EMA's data-based recommendation supports an insufficient rating rather than avoid. The limited term studies do not establish a reliable labor benefit and do not answer questions about earlier pregnancy.
Use while breastfeeding
- Source A says
- NCCIH says the evidence about use while breastfeeding is not conclusive and notes a change in breast-milk fatty acids. (NCCIH: Evening Primrose Oil)
- Source B says
- EMA says use during lactation is not recommended because data are insufficient; LactMed reports no published infant-level information as of its revision date. (European Union herbal monograph on Oenothera biennis or Oenothera lamarckiana oil, LactMed: Evening Primrose)
- Why they differ
- NCCIH describes limited human experience, while EMA's monograph gives a data-based recommendation against use. LactMed and the primary trial abstract provide milk-composition information but do not establish infant exposure or clinical outcomes.
- Other sources
- The Cant et al. 1991 abstract reports a milk-composition trial in 39 women; it does not report infant blood levels or infant clinical outcomes. (Cant et al., 1991 placebo-controlled lactation trial)
- What the evidence shows overall
- The available evidence supports insufficient rather than compatible or avoid: EMA's recommendation is based on missing data, and human evidence is limited to milk-composition measurements.
How to interpret reported labor complications
- Source A says
- Dove and Johnson's 1999 retrospective study said oral EPO may be associated with higher rates of prolonged rupture of membranes, oxytocin augmentation, arrest of descent, and vacuum extraction. (Dove and Johnson, 1999 oral evening primrose oil study)
- Source B says
- NCCIH says reported side effects from attempts to start labor have mostly been mild. (NCCIH: Evening Primrose Oil)
- Why they differ
- The retrospective study reports possible differences in specific labor events, while NCCIH gives a broad summary of reported side effects and does not discuss those outcomes. The statements do not establish the same endpoints or prove cause.
- Other sources
- A 2018 randomized trial did not find differences in need for labor induction or augmentation; it did not resolve every event reported in the retrospective study. (Kalati et al., 2018 randomized clinical trial of evening primrose oil and labor)
- What the evidence shows overall
- The 1999 findings remain a possible association, not proof of cause or a measured risk. The available trials do not establish a reliable labor benefit.
Not enough research found yet.
General research, not specific to pregnancy.
For adults outside pregnancy and breastfeeding, NCCIH says there is not enough evidence to support evening primrose oil for a health condition and lists mainly gastrointestinal side effects with oral use. EMA lists gastrointestinal symptoms, headache, and hypersensitivity reactions among reported effects for its oral herbal medicinal product; their frequency is not known.
- NCCIH lists abdominal pain, nausea, or diarrhea as common side effects of oral evening primrose oil. (NCCIH: Evening Primrose Oil)
- EMA lists indigestion, nausea, softening of stool, increased temperature, hypersensitivity reactions such as rash, and headache; frequency is not known. (European Union herbal monograph on Oenothera biennis or Oenothera lamarckiana oil)
- NCCIH says evening primrose oil is probably not more effective than placebo for breast pain. (NCCIH: Evening Primrose Oil)
- NCCIH: Evening Primrose OilUS governmentSecondaryIndependent check
- European Union herbal monograph on Oenothera biennis or Oenothera lamarckiana oilEU agencySecondaryPage dated 2018-06-05Independent checkEuropean guidance
- Hutcherson et al., 2022 systematic review of evening primrose preparations for parturitionUS governmentPrimary
- Shahinfar et al., 2023 systematic review and meta-analysis of evening primrose oilUS governmentPrimaryIndependent check
- Dove and Johnson, 1999 oral evening primrose oil studyUS governmentPrimaryIndependent check
- Kalati et al., 2018 randomized clinical trial of evening primrose oil and laborUS governmentPrimaryIndependent check
- Niazi et al., 2026 systematic review and meta-analysis of oral and vaginal evening primrose oilPrimaryIndependent check
- LactMed: Evening PrimroseUS governmentSecondaryPage dated 2021-05-17
- Cant et al., 1991 placebo-controlled lactation trialUS governmentPrimaryIndependent check
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.
Related
- Borage Oil
- Chasteberry (Vitex)