Evening primrose oil for cervical ripening prior to labor induction in post-term pregnancies: A randomized controlled trial

Abstract

Cervical ripening can be induced using a variety of methods. It is used in cases where the cervix is in an unfavorable state prior to the start of the labor induction. The purpose of this study was to investigate how vaginal administration of evening primrose oil (EPO) affects cervical ripening in women who were scheduled for labor induction. This randomized controlled trial was conducted from November 2018 to December 2019. The inclusion criteria were as follows: age 18-35 years old, first pregnancy, a live singleton baby with a cephalic presentation, gestational age≥ 41 weeks, intact membranes, normal cardiotocography, and a Bishop score of ≤ 4. Two hundred women were randomly assigned to a single vaginal dose of 1000 mg evening primrose oil (n=100) or placebo (n=100). Any change in Bishop score was considered the primary outcome variable in the efficacy evaluation. Of 200 eligible women, 25 women were excluded for various reasons. Finally, statistical analysis was performed on 175 women (88 women in the experimental group and 87 in the control group). At baseline there was no significant difference between the two groups in Bishop score. However, after the intervention, this score was significantly higher in the experimental group than in the control group (Mean Difference: 3.29, 95% Confidence Interval: 3.51 to 1.18). No adverse effects were observed or reported. Vaginal application of EPO at a single dose of 1000 mg at 41 weeks gestation improved Bishop score and reduced parturition time in post-term pregnancies. Iranian Registry of Clinical Trials (IRCT20181107041585N3).