Ways to Induce Labor Part 5: Evening Primrose Oil

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Evening Primrose Oil (EPO) is a supplement that is commonly recommended as a “natural” induction method, but is it safe? Does it work? What does the evidence say?

Disclaimer: None of these methods should be used unless recommended by your provider, not even the natural methods. “Natural” does not automatically mean risk free. Some common recommendations are evidence based; others are passed on as old wive’s tales and are ineffective or possibly harmful. Normal, low risk pregnancies should not be induced prior to 39 weeks, and ideally not before 41 weeks, without a medical indication. Healthy babies will come when they are ready; taking the baby too soon can result in breathing and feeding difficulties, as well as increase the risk of c-section. Being uncomfortable, having difficulty sleeping, multiple rounds of false labor, or excitement for the baby to come are NOT reasons to induce. That being said, there are times when induction is appropriate, and this decision should be made with your provider.


Evening Primrose Oil (EPO) is an herbal supplement made from the seeds of a flowering plant. It comes in capsule form. In pregnant women, it is traditionally used either orally or inserted vaginally and is purported to help induce labor. Even though it comes up frequently, even casually, when anyone asks for natural ways to start labor, EPO is not well studied. Is it even safe to use? If it is, then does it do what people say? Can you take EPO to induce labor? Or, is it just an “old wive’s” suggestion that doesn’t actually work?


There are only 2 studies available studying  EPO’s effect on pregnancy and labor.


Dove, D. and Johnson, P. (1999). Oral evening primrose oil: its effect on the length of pregnancy and selected intrapartum outcomes in low risk nulliparous women. Journal of Nurse Midwifery (3) 44

    From the abstract: “The purpose of this study was to investigate the effect of oral evening primrose oil on the length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women. A two group retrospective quasi-experimental design conducted on a sample of women who received care in a birth center, compared selected outcomes of 54 women taking evening primrose oil in their pregnancy with a control group of 54 women who did not. Findings suggest that the oral administration of evening primrose oil from the 37th gestational week until birth does not shorten gestation or decrease the overall length of labor. Further, the use of orally administered evening primrose oil may be associated with an increase in the incidence of prolonged rupture of membranes, oxytocin augmentation, arrest of descent, and vacuum extraction.”

    This study showed that the use of oral EPO from 37 weeks until birth was not successful in inducing labor, and also did not make labor any shorter. The study also found an increased likelihood of prolonged rupture of membranes, pitocin used to augment labor, failure to progress, and use of the vacuum for delivery. Not only did it not work at inducing labor as it was intended, it also may potentially cause harm.

    It is important to note that this study is old by research standards, done in 1999, and has a small sample size. They only studied oral EPO, not vaginal. They also only looked at its effects on patients having their first baby, not women who have already had a pregnancy or birth. Another weakness is that the type of study design does not show causation, only association, and was not randomized or double blind. We can not say that EPO caused the complications, only that it’s use is associated with increased rates of the complications.


Ty-Torredes, K. (2006). The effect of oral evening primrose oil on bishop score and cervical length among term gravidas. American Journal of Obstetrics and Gynecology. 6(195).

    The objective of this study was, “To determine if treatment with Evening Primrose Oil (EPO) at a dose of 1 capsule given thrice daily for 1 week shows a greater effect on Bishop score by internal examination and cervical length on transvaginal ultrasound compared to placebo among term gravidas awaiting onset of labor.” It was a randomized controlled double blind placebo controlled trial with 71 subjects. Patients took one 500mg capsule three times a day for 1 week. Effect on the fetus was tested using a nonstress test and modified biophysical profile, as well as measuring birth weights; fetal testing was normal before and after treatment in both groups, and babies birth weights were equivalent in both groups. There were no differences in time to beginning of labor in either group; the EPO was not effective at actually inducing labor. It was, however, found to significantly increase bishop score and decrease cervical length. This effect was greatest in first time moms, as well as in those past 39 weeks. While there was no significant increase in likelihood of labor, or in decreased length of labor in the EPO group, there was a significantly higher percentage of women who delivered vaginally in the treatment group (70% vs 51%).

    The major strength of this study is its design: a randomized controlled double blind placebo study. This is the gold standard of research. It be concluded that the EPO caused the increased bishop score and decreased cervical length. It can be reasonably concluded that the EPO did not cause labor, at least not at the dosage or route used in the study. This study did NOT show an increased need for pitocin augmentation, unlike the first study.

    The biggest weakness of the study is its small sample size, particularly at demonstrating safety. With only 71 subjects total in the study, it is difficult to determine if more differences in fetal testing would have been shown with a larger sample size. They also did not measure intrapartum complications of the EPO group, so it is unknown if there are differences here that were not studied. This study is more recent than the first, but is still dated by research standards at 10 years old.


Though limited, the research clearly shows that EPO is NOT effective at inducing labor in first time mothers. It is unknown if it would be more successful at inducing labor in people who have had babies before. However, it was an effective cervical ripener, particularly after 39 weeks and in first time mothers. This means that it may have some merit when used in combination with other methods to improve bishop score and increase the likelihood of a successful induction should it be necessary. In the second study, it also increased the likelihood of the patient having a successful vaginal delivery.

My main concern with EPO is its safety in pregnancy and potential for causing labor complications. In the first study, there was a definite association with intrapartum complications including prolonged rupture of membranes, failure to progress, and vacuum delivery (it is important to note that this was an association, and does not mean that we can say that EPO use CAUSED these things). The second study did not measure these complication rates, so it is difficult to say whether they would have found the same results. The second study did counter the first in that there was no difference in need for pitocin augmentation between groups. It is reassuring that the second study did not find differences in NSTs and biophysical profiles between groups. However, the EPO was only used for 1 week at a small dose of 1500mg a day. In practice, it is commonly used for weeks at a time at much higher doses. It was also only studied orally, and it is commonly used vaginally. It is impossible to say at this time if increased complications would have been found if the “traditional” dosing was used.

EPO should NOT be recommended for LABOR INDUCTION at this time, especially in first time mothers. It is at best ineffective for getting someone into labor. More study is needed before EPO can be recommended as a cervical ripener in pregnancy, especially at the traditional dosage of 3000mg daily starting at 37 weeks and continuing until delivery. It was an effective cervical ripener after only 1 week of use at 1500mg daily, and this was the length of time it was found to be “safe”. To minimize the potential risks, and still get the benefits of cervical ripening, it should not be used until ideally 40-41 weeks, and only if the cervix is still unfavorable. It does nothing to shorten the length of pregnancy, so taking it sooner and for a longer period will do nothing except increase possible risks. If a patient goes into labor before then, no additional “help” is needed – the body is working just as intended. If there is a 42 week “deadline” that a patient must have delivered by, and the cervix is still unfavorable at 40-41 weeks, then it may be worth starting the EPO in preparation for possible induction. If the cervix is favorable, there is no additional benefit to taking the EPO. EPO should only be used under the guidance of a trained provider.

It is important to note that EPO is also used as a blood thinner in non-pregnant patients. Pregnant patients who are at risk of hemorrhage after delivery should NOT use EPO. It may potentially increase the risk of bleeding or hemorrhage after birth.

Just because EPO is “natural” or “has always been used that way” is not a reason to continue. Just as the obstetricians are held to a standard that says they should change their practice based on new research recommendations, so should midwifery. There are plenty of examples of dated practices being continued in obstetrics that are either not helpful, or directly harmful (for example, routine continuous fetal monitoring). People become angry at these practices, and rightfully so. This same standard for evidence based care needs to be applied to midwifery and supplement use.

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