Two randomized trials answer this question and they disagree, because they used 2 different routes, oral and vaginal. That 1 distinction is the whole story.
Taken by mouth, at 1000 mg twice daily for 7 days, it changed nothing. Given vaginally, it shifted the Bishop score by 0.64 points.
Quick Answer: Does Evening Primrose Oil Induce Labour?
The oral form does not, on the best trial available. A triple-blind randomized trial in 80 nulliparous women at 40 weeks gave 1000 mg twice daily for 7 days and found no difference in gestational age at delivery, need for induction or augmentation, labour duration, birth weight or Apgar scores. Cervical ripening is a decision for a midwife or obstetrician.
Key Takeaways
- The oral trial gave 1000 mg twice daily for 7 days.
- It found 0 difference in gestational age, induction need or labour duration.
- Neonatal weight and Apgar scores also showed 0 significant difference.
- A separate vaginal trial raised the Bishop score by 0.64 points.
- Caesarean sections in that trial were 4 against 2, not significant.
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Why This Page Exists
People are asking each other online how much to take and where to put it. That is a question for a maternity team, and it deserves a straight evidence answer rather than silence.
- Who decides: Your midwife or obstetrician, always.
- What we sell: An oral softgel, 1300 mg.
- What the trials used: 2 different routes, with different results.
- What we will not give: A protocol for starting your own labour.
Background on the oil itself is in our evening primrose oil overview.
The Oral Trial
This is the trial that applies to a softgel, and it is the stronger design of the 2.
| Feature | Detail |
|---|---|
| Design | Triple-blind, placebo-controlled, randomized |
| Participants | 80 nulliparous low-risk women, 40 per group |
| Gestational age at entry | 40 weeks, Bishop score under 4 |
| Dose | 1000 mg twice daily for 7 days |
| Gestational age at delivery | No significant difference |
| Induction or augmentation | No significant difference |
| Labour duration, birth weight, Apgar | No significant difference |
Nothing that was measured moved, including every outcome a person hoping to avoid a medical induction would care about.[1]Evening primrose oil and labour, is it effective? A randomised clinical trial — Journal of Obstetrics and Gynaecology (2018) View source Eighty women is a small trial, and it was triple-blinded, which is unusual and good.
The Vaginal Trial
A separate randomized double-blind trial used a different route and did find a difference. Its size is the part worth knowing.
| Outcome | Evening primrose oil | Placebo |
|---|---|---|
| Participants analysed | 48 | 48 |
| Bishop score after | 5.83 | 5.19 |
| Difference | 0.64 points on a 13-point scale | p = 0.002 |
| Oxytocin injection needed | 10.4% | 31.3% |
| Caesarean section | 4 women | 2 women, p = 0.677 |
A 0.64-point shift on a 13-point scale is a real result and a small one, and the caesarean numbers went the other way without reaching significance.[2]The Use of Evening Primrose Oil for Cervical Ripening in Low-Risk Women with Term Pregnancy: A Randomized Double-Blinded Controlled Trial — Complementary Medicine Research (2024) View source We sell an oral softgel, and this trial did not test that.
What This Does Not Tell You
Four things are missing from both trials, and each of them matters more than the headline.
- Safety at scale: 176 women in total across both trials.
- Who is low risk: Both recruited low-risk pregnancies only.
- Timing: Neither supports self-starting before term.
- Route: The oral result and the vaginal result are not interchangeable.
The wider safety picture, including bleeding risk, is in the safety cautions.
The Position We Take
It is short, and it is the same one a maternity unit would give.
| Question | Our answer |
|---|---|
| Should I use this to start labour? | That is a decision for your midwife or obstetrician |
| Will an oral softgel bring on labour? | The trial that tested it found no difference |
| Should I use it vaginally? | Not on our advice, and not without your maternity team |
| When should I call? | Reduced movements, bleeding, fluid loss or regular contractions |
Amounts used across all the evening primrose trials, in and out of pregnancy, are compared in dosage and timing.
- Outside pregnancy: An ordinary seed oil supplement.
- Evidence base: Modest, and mostly 2 narrow uses.
- In pregnancy: A maternity conversation, not a purchase.
A 2024 systematic review of this oil concluded the literature is highly heterogeneous and fails to support strong recommendations for any of its 12 tested conditions.[3]The effect of Oenothera biennis (Evening primrose) oil on inflammatory diseases: a systematic review of clinical trials — BMC Complementary Medicine and Therapies (2024) View source That applies to our 1300 mg softgel as much as to any other.
Contact Your Maternity Unit Immediately Rather Than Waiting If
- Any plan to use evening primrose oil to start labour or ripen the cervix without your midwife or obstetrician deciding it, including vaginal use
- Reduced fetal movements, bleeding, fluid loss or regular painful contractions in pregnancy
- Taking warfarin or any anticoagulant or antiplatelet medicine
- A seizure disorder, or taking phenothiazine medicines
- A new breast lump, skin change or nipple discharge
Frequently Asked Questions
Does primrose make you go into labor? +
The oral trial found no difference in gestational age at delivery across 80 women. It is not an induction method.
How much evening primrose oil to induce labor? +
We do not give an amount for this. The trial that tested 1000 mg twice daily for 7 days found 0 difference in any outcome.
Can primrose oil cause contractions? +
The oral trial measured labour onset across 80 women and found no difference. Regular painful contractions are a reason to contact your maternity unit, whatever you have taken.
What does evening primrose oil do to your cervix? +
In 1 vaginal trial the Bishop score was 0.64 points higher than placebo, at 5.83 against 5.19. That is a small shift on a 13-point scale.
Will primrose oil help me dilate? +
Dilation was not the measured outcome; the Bishop score was, and it moved 0.64 points. Cervical ripening decisions belong with a midwife or obstetrician.
When to start inserting primrose oil for labor? +
We do not advise vaginal use, and we give no timing for it. That is a conversation with your maternity team rather than 1 to have online.
Is evening primrose oil safe in pregnancy? +
Both trials recruited low-risk pregnancies and together covered 176 women. That is too small a base for a general safety statement.
Did the vaginal trial reduce caesareans? +
No. There were 4 caesareans in the evening primrose group against 2 on placebo, which was not statistically significant.
Does it shorten labour? +
The oral trial measured the duration of every stage and found no significant difference between the 2 groups.
What helps dilate your cervix faster? +
Established methods are clinical ones, chosen by your maternity team. No supplement has evidence approaching those 2 or 3 options.
Why do midwives mention it then? +
It is a long-standing traditional practice, and 1 vaginal trial did find a small Bishop-score difference. Practice varies, which is why it is a conversation.
Can I take it after the birth? +
There is no trial of that, and 0 evidence either way. Anything taken while breastfeeding is worth raising with your midwife or health visitor.
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