Many moms and midwives use evening primrose oil (EPO) for cervical ripening. So I was absolutely shocked at the complete lack of evidence on the effectiveness and safety of EPO use among pregnant women.
There are only two studies that examine the oral use EPO and its ability to ripen the cervix during pregnancy. There are no studies on the vaginal use of EPO. In short, there is insufficient clinical evidence documenting the risks and benefits of EPO and without that information, the question is, should pregnant women take it?
The available evidence on EPO
Paula Senner gives an excellent review of the first study (Dove 1999) in her Quantitative Research Proposal entitled, “Oral Evening Primrose Oil as a Cervical Ripening Agent in Low Risk Nulliparous Women” (emphasis mine),
The study group consisted of 54 women who took oral evening primrose oil in their pregnancy (500 mg three times a day starting at 37 weeks gestation for the first week of treatment, followed by 500 mg once a day until labor ensued), and the control group was composed of 54 women who did not take anything. Antepartum and intrapartum records of all women were reviewed focusing on the above identified criteria.
Results showed no significant differences between the evening primrose oil group and the control group on age, Apgar score, or days of gestation (P>.05)… This retrospective chart review showed no benefit from taking oral evening primrose oil for the purpose of reducing adverse labor outcomes or for reduction of length of labor.
The study’s abstract gives us more details on the its findings (emphasis mine):
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 [Pitocin] augmentation, arrest of descent, and vacuum extraction.
The second study found that while women who took EPO experienced a greater degree of cervical ripening, that did not result in a shorter pregnancy or labor: “There was no significant difference in the interval from onset or end of treatment to onset of labor between the two groups” (Ty-Torredes, 2006).
So one study on oral EPO found that it doesn’t work as we thought it did and it offers considerable risks. The other study found that it does result in some cervical ripening, but that did not translate into shorter pregnancies or labors.
As a result, a December 2009 article published in the American Family Physician recommended,
The use of evening primrose oil during pregnancy is not supported in the literature and should be avoided.
Medline Plus, a website published by the US National Library of Medicine and the National Institutes of Health, published an April 2012 article on EPO. Medline echoes the sentiments of the American Family Physician article when it said there was,
insufficient evidence to rate effectiveness for [EPO during pregnancy and] research to date suggests that taking evening primrose oil doesn’t seem to shorten labor, prevent high blood pressure (pre-eclampsia), or prevent late deliveries in pregnant women… [Further,] taking evening primrose oil is POSSIBLY UNSAFE [their emphasis] during pregnancy. It might increase the chance of having complications. Don’t use it if you are pregnant [emphasis mine.]
Bleeding issues could complicate cesareans
Research on the use of EPO for other aliments among non-pregnant people has suggested there could be a possible association between the use of EPO and bleeding problems during surgery.
As a result, Medline recommends that people don’t use it at least 2 weeks before a scheduled surgery.
This poses a special problem for women using EPO during the last weeks of pregnancy. Since we cannot predict who will have a vaginal birth and who will have a cesarean, it is important to consider that EPO could contribute to hemorrhage during a cesarean and possibly even during a normal vaginal delivery.
We just don’t know because there is a lack of data.
Dosages and mode of delivery
Another hole in the research and our knowledge relates to dosage.
I see women reporting an incredible range of dosages on the internet. What is safe?
There are no clinical studies documenting how much women should take. Maybe X dose of EPO is good, but Y dose introduces XYZ risks.
How long should women take EPO? The last month of pregnancy? The last two weeks? (Remember, we just read how there is a possible bleeding issue.)
Should they take it twice a day or once a day? Does the body absorb or metabolize EPO differently if it is administrated vaginally or orally?
We just don’t know the answers to these questions.
What about our bodies’ innate ability to birth?
It comes down to the fundamental question: Do our bodies need something to help us go into labor?
Many natural birth advocates reject the routine use of Pitocin augmentation during labor because they say our bodies know how to birth. Yet it’s often women from this same mindset that use EPO.
Either pregnant people as a whole need something to help them go into labor – whether that is EPO or Pitocin – or they don’t.
Are we less leery of EPO because it comes from a flower? Because it’s not produced by “big pharma?”
Because midwives suggest it more than OBs?
Because we can purchase it over the counter? Because it’s a pill, not an injection? Because we can administer it to ourselves in the comfort of our home?
Because it is used so routinely that no one questions it? Or is it simply because we all assume since everyone takes it, the evidence must be on the side of EPO?
On (the lack of) evidence: Holding ourselves to the same standard
When I have shared the lack of evidence on EPO’s ability to ripen cervi or prepare a woman’s body for labor, sometimes women reply with “But there is no evidence to suggest it won’t help either.”
American OBs used this same rationale when they induced scarred moms with Cytotec in the 1990s. There were no published medical studies on Cytotec induction in scarred women, so we didn’t know the risks and benefits. But people used it because we knew it caused uterine contractions. What can go wrong, right?
But the problem is, when there is a lack of clinical evidence on large populations of women, we are sometimes surprised with dire outcomes that no one could have predicted as was the case of Cytotec.
We cannot look back at that period and think, “How could they have done that” when we are now doing the same thing with EPO: using a chemical without evidence of its benefits and harms.
Some rail against “the medical system” because Pitocin/ultrasound/etc hasn’t been “proven safe,” yet we use EPO with no evidence that it does what we think it does, no evidence that it is safe, and the limited evidence we do have says that it’s associated with a variety of complications.
As Hilary Gerber D.O. aka Mom’s Tin Foil Hat says,
As someone who spent many years in the natural supplements industry, I agree that we need to hold natural products to the same scrutiny.Also, most EPO is extracted with solvents like hexane. I am much more supportive of natural products or interventions that have been used in that form or method for generations (e.g. sexual intercourse at term, ingesting a substance that is a common food item, etc) than a chemically extracted, concentrated, unstudied substance.
Anecdote vs. evidence
OBs who used Cytotec on women with a prior cesarean in the 1990s inevitably would have said, “I haven’t had a bad outcome yet,” and I suspect that many people who use EPO now would say the same thing.
When we have one woman who used EPO and had an arrest of descent, do care providers recognize that this could be as a result of the EPO?
When we have one women who used EPO and it worked as expected, how can we determine her labor progressed because of the EPO?
When you have a small sample size, it’s hard to make a connection. It’s even more difficult to connect EPO to it’s possible list of complications when not many care providers are aware of the lack of evidence on EPO and the findings of this one lone study.
Is our limited experience, with relatively few patients, without meticulous record keeping that can detect patterns across groups of patients, sufficient evidence? I don’t think so.
We would likely need thousands of women in order to create a sample size powerful enough to detect – or rule out – common and more rare EPO complications in addition to answering the many questions I posed above.
Take away message
I’m not saying to use EPO or not.
I’m simply pointing out how little we know about this commonly used substance and questioning if that should make a difference in how we view and/or use it.
There is limited evidence on EPO’s ability to ripen the cervix and aid with labor. We have two studies on the oral use of EPO that looked at this question and none on the vaginal use of EPO among pregnant women.
One study found that EPO doesn’t ripen the cervix and poses considerable risk. Another study found that EPO does ripen the cervix but those women did not go into labor sooner than the women that didn’t take EPO.
We have no evidence on an appropriate or safe dosage (if that exists).
We have no evidence on the risks and benefits of oral vs vaginal administration.
In order to make the association between EPO and complications, care providers need to be aware of the complications with which EPO may be associated.
We need more large studies to confirm or refute the notion that EPO = ripen cervix = shorter pregnancies. Without that information, we are using a product that we know very little about.
Bayles, B., & Usatine, R. (2009, Dec 15). Evening Primrose Oil. American Family Physician, 80(12), 1405-1408. Retrieved from http://www.aafp.org/afp/2009/1215/p1405.html
Dove, D., & Johnson, P. (1999, May-Jun). Oral evening primrose oil: its effect on length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women. Journal of Nurse-Midwifery, 44(3), 320-4. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10380450
Gerber, H. (2012, November 13). Facebook comments on evening primrose oil.
McFarlin, B. L., Gibson, M. H., O’Rear, J., & Harman, P. (1999, May-Jun). A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. Journal of Nurse Midwifery, 44(3), 205-16. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10380441
Medline Plus. (2012, Apr 10). Evening primrose oil. Retrieved from Medline Plus: A service of the U.S. National Library of Medicine & National Institutes of Health: http://www.nlm.nih.gov/medlineplus/druginfo/natural/1006.html
Senner, Paula. (2003, December). Oral Evening Primrose Oil as a Cervical Ripening Agent in Low Risk Nulliparous Women. Retrieved from Frontier School of Midwifery and Family Nursing, Philadelphia University: http://www.instituteofmidwifery.org/MSFinalProj.nsf/a9ee58d7a82396768525684f0056be8d/f44c26c0836acbb585256dd1006b2a22?OpenDocument
Ty-Torredes, K. A. (2006). The effect of oral evening primrose oil on bishop score and cervical length among term gravidas. AJOG, 195(6), S30. Retrieved from http://www.ajog.org/article/S0002-9378%2806%2901323-8/fulltext
Wagner, Marsden. (1999). Misoprostol (Cytotec) for Labor Induction: A Cautionary Tale. Retrieved from Midwifery Today: http://www.midwiferytoday.com/articles/cytotecwagner.asp