Evening primrose oil (EPO) is an herbal supplement derived from the seeds of the Oenothera biennis plant. It is often sought out by individuals in the final weeks of pregnancy as a potential method to prepare the body for labor. The primary goal of using EPO is to encourage cervical ripening, which is the process of softening and thinning the cervix before contractions begin. This preparation promotes a smoother transition into the active stages of labor.
The Mechanism of Cervical Ripening
The effectiveness of evening primrose oil in labor preparation is rooted in its biochemical composition, specifically its concentration of essential fatty acids. EPO contains linoleic acid, an omega-6 fatty acid, which the body metabolizes into Gamma-Linolenic Acid (GLA). GLA acts as a precursor for certain hormone-like compounds.
This GLA is eventually converted into prostaglandins, particularly prostaglandin E2 (PGE2). Prostaglandins are naturally produced by the body and are responsible for the physical changes that allow the cervix to dilate. When applied or ingested, the resulting increase in these compounds is thought to chemically soften, thin, and efface the cervix, preparing it for the mechanical forces of labor. A favorable, or “ripe,” cervix is generally more responsive to contractions.
Recommended Gestational Timing for Initiation
The timing of when to begin using evening primrose oil is a primary consideration for pregnant individuals. Recommendations suggest that EPO should only be initiated once a full-term or near-term gestation has been reached, typically defined as starting no earlier than the 36th week of pregnancy.
This strict timing avoids unintended stimulation or change to the cervix before the baby is fully mature. Initiating a substance that encourages cervical ripening too early could increase the risk of preterm labor. Most sources recommend waiting until 37 weeks, when the pregnancy is officially considered early term, before beginning any regimen.
Application Methods and Suggested Dosages
Evening primrose oil can be administered through two primary routes. The first method is oral ingestion, where capsules are swallowed, often starting with a dosage of 500 to 1000 milligrams once or twice daily. This allows the oil to be absorbed through the digestive system before circulating throughout the body.
The second method is vaginal insertion. For this application, one or more capsules, typically 1,000 mg to 2,000 mg total, are inserted high into the vagina near the cervix, usually at bedtime. Some individuals puncture the capsule with a sterile pin before insertion to release the oil directly onto the cervical tissue. Regardless of the method, it is advisable to start with a minimal dose and consult with a healthcare provider before beginning any supplement regimen in late pregnancy.
Clinical Evidence and Safety Warnings
Despite its use as a traditional remedy, the clinical evidence supporting evening primrose oil’s effectiveness in shortening labor or promoting a faster delivery remains inconsistent. Some studies have suggested that the vaginal application of EPO may lead to a more favorable Bishop score, which is a measure of cervical readiness, potentially reducing the need for medical induction. Conversely, other randomized controlled trials have found no difference in labor duration, gestational age at delivery, or the need for medical augmentation between those who used EPO and those who did not.
More concerning are the potential risks associated with its use, particularly because it is an unregulated herbal supplement. Because EPO can influence the body’s prostaglandin pathways, it may carry a risk of increasing bleeding or acting as a blood thinner. Individuals with known bleeding disorders, those on anticoagulant medications, or those with placenta previa should strictly avoid using the oil. Furthermore, some research has indicated a possible association with a prolonged rupture of membranes or an increased incidence of oxytocin use.