Cervical Ripening

Overview

Evening Primrose Oil is the primary supplement studied for cervical ripening, with eight trials. Most research suggests oral or vaginal use in late pregnancy may soften the cervix, shorten labor, and lower cesarean delivery rates at studied doses and schedules.

Typical regimens ranged from 500 to 4500 mg daily starting around 37 weeks for 7–10 days, or a single pre-labor dose. Effects on later labor stages, need for induction drugs, and infant weight are less consistent across studies. See the evidence reviews below for dosing and outcome details.

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Evening Primrose Oil	★★★★★	Medium

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Evidence Review

Most studies show that taking evening primrose oil by mouth or vaginally in late pregnancy can help the cervix soften and ready for labor, and may shorten labor and lower the chance of cesarean delivery.
Taking 500 to 4500 mg daily starting around 37 weeks for 7 to 10 days, or as a single dose close to labor, can reduce labor time and cesarean risk by up to 39%.
Evening primrose oil does not seem to change the second phase of labor, need for labor drugs, or baby weight.
Studies disagree on whether it improves baby’s Apgar scores at birth.
Some studies show vaginal evening primrose oil helps prepare the cervix better than placebo or even some medicines.
However, one small study suggested that taking evening primrose oil from 37 weeks until birth may not help and could be linked to longer labor and more need for labor drugs.

Browse 8 studies3 meta-analyses

RCTThe Use of Evening Primrose Oil for Cervical Ripening in Low-Risk Women with Term Pregnancy: A Randomized Double-Blinded Controlled Trial2024n=48

In 48 low-risk term pregnancies per group, daily 1,000 mg vaginal evening primrose oil significantly raised post-intervention Bishop score (5.83 vs 5.19) versus placebo, without significant differences in cesarean rates.

Effect: Benefit
Dose: 1000 mg/day
Population: Women
Participants: 48

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RCTComparative Study of the Effect of Vaginal use of Primrose Oil with Misoprostol on Cervical Preparation of Prim Gravid Women: A Double-blind Clinical Trial2023n=55

In 110 primigravid women at ≥40 weeks, vaginal evening primrose oil 1,000 mg versus 25 µg misoprostol significantly increased post-intervention Bishop score and differed on cervical ripening and labor induction outcomes.

Effect: Benefit
Dose: 1000 mg/day
Population: Women
Participants: 55

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RCTThe effect of evening primrose oil on cervical ripening and birth outcomes: A systematic review and meta-analysis2023n=920

A meta-analysis of 5 high-heterogeneity studies including 652 participants found that evening primrose oil was effective for cervical ripening. Both oral and vaginal use of evening primrose oil significantly increased Bishop score relative to placebo. [10709]

Effect: Benefit
Population: Women
Participants: 920

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MetaEvening primrose oil for cervical ripening in term pregnancies: a systematic review and meta-analysis2021

A meta-analysis of 9 high-heterogeneity studies found that evening primrose oil was effective for cervical ripening, shortening the duration of labor and reducing the risk of cesarean section compared to placebo. [10710]

Effect: Benefit

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MetaThe effect of evening primrose oil on labor induction and cervical ripening: A systematic review and meta-analysis2021

A meta-analysis of 4 trials found no significant difference in Bishop score change with evening primrose oil versus control for cervical ripening (SMD 0.27, 95% CI crossing null) despite high heterogeneity (I² 91.4%).

Effect: No Benefit
Population: Women

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RCTEvening primrose oil and labour, is it effective? A randomised clinical trial2018n=80

In 80 nulliparous women at 40 weeks (Bishop score <4), 1,000 mg evening primrose oil twice daily for 7 days did not change gestational age at delivery, labor duration, induction needs, or neonatal outcomes versus placebo.

Effect: No Benefit
Duration: 7 days
Dose: 1000 mg/day
Population: RA patients
Participants: 80

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The effect of oral evening primrose oil on bishop score and cervical length amongst term gravidas2006

A clinical study in term pregnant women evaluated oral evening primrose oil for effects on Bishop score and cervical length, assessing whether supplementation alters cervical readiness markers before labor.

Population: Women

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RCTOral evening primrose oil: its effect on length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women1999n=54

In 54 nulliparous women taking oral evening primrose oil from 37 weeks versus 54 controls, gestation length and overall labor duration were unchanged; EPO use was associated with more prolonged rupture of membranes and assisted deliveries.

Effect: No Benefit
Population: Women
Participants: 54

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Study distribution across 1 supplements for cervical ripening (8 studies total).
Supplement	DEX	Studies	Meta-analyses	Share
Evening Primrose Oil	★★★★★68%	8	3	100%

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