Evening Primrose versus Misoprostol for Cervical Dilatation before Gynecologic Surgeries; a Double–blind Randomized Clinical Trial

Cervical ripening/dilatation is necessary for gynecologic procedures, but pharmacological dilators have several adverse effects. In this regard, evening primrose oil (EPO) has been shown as an effective dilator, though it has few complications. This randomized clinical trial (RCT) aimed to compare the effect of EPO and misoprostol on cervical ripening/dilatation.

In this double–blind RCT study, women of reproductive age without history of normal vaginal delivery (NVD) and menopause women (age range: 20–75 years) were enrolled. The subjects who were candidates of hysteroscopy, dilatation, and curettage were randomly assigned into two groups. In one group, 2 capsules of 500 mg EPO (N=81) and in the other group 2 capsules of 200 µg misoprostol (N=84) were placed in posterior fornix 2 hours before surgery. The time to reach complete dilatation (Hegar 3 to 10 mm), size of the first Hegar used to apply force, bleeding volume, and cervical laceration were compared between the groups using the IBM SPSS Statistics for Windows, Version 21.0 (Armonk, NY: IBM Corp).

The two study groups had similar demographic information, number of pregnancies, cesarean sections, and NVDs (P>.05), but had different frequency of surgical types (P=.018). EPO group had a larger mean size of the Hegar (7.32 vs. 6.58 mm; P=.004) and shorter time to reach complete dilatation (242.35 vs. 331.79 min; P=.002); however, bleeding volume and frequency of cervical laceration were not different between the groups (1.41 vs. 2.00 cc and 8.6% vs. 14.3%, respectively; P>.05).

The superiority of EPO capsules to misoprostol for cervical ripening before gynecologic procedures in women of reproductive age without history of normal NVD and menopause women suggests it as an appropriate alternative to misoprostol.