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The Efficacy of Evening Primrose Oil as a Cervical Ripening Agent for Gynecologic Procedures: A Single-Blinded, Randomized Controlled Trial

Rusienne Mae A. Verano, MD; Mary Girlie Veloso-Borromeo, MD, FPOGS
Department of Obstetrics and Gynecology, Cebu Doctors Hospital

Background: Evening Primrose Oil (EPO) is one of the most commonly prescribed cervical ripening agents. Cervical ripening is the softening, effacement, and dilation of the cervix that occur prior to active labor, and is an intervention that is used for certain indications, such as postdates pregnancy. There are gynecologic cases wherein the cervix is closed and dilatation has not occurred making the procedure difficult. In studies, EPO works by softening and ripening the cervix in the pregnant woman. More likely it has the same effects in a non-pregnant patient with regards to softening and dilating the cervix during gynecologic procedures.

Methods: The study was conducted in a tertiary hospital. Patients scheduled for gynecologic procedures were randomly grouped under the control and study group. Both groups had an internal examination during admission. The study group, in addition, were given EPO 4 capsules intra-vaginally, 6 hours prior to the contemplated procedure. Cervical characteristics were assessed initially on admission and pre-proedure.
Consistency were assessed using the Consistency Index (CI) and graded as firm=1, medium=2 and soft=3. Dilatation were assessed using the Dilatation Index (DI) and graded as closed=1, admits tip =2 , >1cm= 3. Pre-procedure, cervical characteristics and the CDI of both groups were assessed. Hegars dilators were used to assess the degree of dilatation, noting the diameter of dilator that can be introduced freely, and to what diameter the cervix can be maximally dilated.

Results: 80 patients were enrolled in the study; 39 patients were assigned in the control group and 38 patients were assigned in the study group (3 were excluded). In the study group, their DI improved by 36.2% (pre = 1.53+/-0.51 to post = 2.08+/-0.49) (p<0.001), CI increased by 115.9% (pre=1.16+/-0.37 to post = 2.50+/-0.65) (p<0.001), and their CDI changed by 70.6% (pre=2.68+/-0.74 to post = 4.58+/-0.95) (p<0.001). The changes of scores in all the cervical parameters in the study group were statistically significant.

Conclusion: EPO 4 capsules punctured and administered intra-vaginally 6 hours prior to contemplated gynecologic procedure can promote cervical ripening as exhibited by the improvement of the CDI from initial assessment to pre-procedure assessment.