The Effect of Vaginal Consumption of Evening Primrose Oil on Cervical Preparation and Labor Progress in Term Pregnancy: A Randomized Clinical Trial

Document Type : Original Article

Authors

1 Associate Professor, Department of Obstetrics and Gynecology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

2 Resident, Department of Obstetrics and Gynecology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

3 Assistant Professor, Department of Emergency Medicine, Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnourd, Iran.

4 Librarian, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

10.22038/ijogi.2025.59660.4966

Abstract

Introduction: Cervical preparation is prerequisite for successful natural childbirth. Various studies have reported different effects of evening primrose oil on cervical preparation, which were sometimes positive and sometimes ineffective. The present study was conducted with aim to investigate the effect of taking evening primrose oil as an outpatient basis on cervical preparation in term pregnancy.
Methods: This clinical trial study was conducted in 2020 on 76 pregnant women with gestational age of 40 weeks referred to the teaching hospitals of Mashhad. The subjects were placed in two groups of case and control (n=38 per group). For the intervention group, after determining the bishop and stripping, one vaginal primrose capsule was implanted and the drug was repeated every 6 hours. The control group underwent only stripping after the initial examination and determination of the bishop, and both groups were followed up within 24 hours. Secondary bishop score, latent and active phase of labor, duration of labor, type of labor, 1- and 5-minutes Apgar score and postpartum hemorrhage were assessed in both groups. Data analysis was performed using SPSS software (version 26) and t-test, chi-square, and Fisher's exact tests. P<0.05 was considered significant.
Results: The secondary bishop score in the intervention group was significantly higher than the control group (7.66±1.02 and 4.39±0.790, respectively) (P<0.001), also the duration of the latent phase in the intervention group was significantly lower than the control group (7.53±1.85 and 14.28±3.68 hours, respectively) (P<0.001). The active phase of labor was also significantly lower in the intervention group than the control group (2.69±0.98 and 4.28±1.21 hours, respectively) (P<0.001). There was no statistically significant difference between the intervention and control groups in delivery time (18.61±5.8 and 20.78±9.66 minutes, respectively) (P=0.243). These results were similar among non-primiparous women. Among primiparous women, except for the duration of labor, which was significantly reduced in the intervention group compared to the control group (22.14±6.71 and 30.71±4.74 minutes, respectively) (P=0.001), other results were similar.
Conclusion: The use of evening primrose vaginal capsule is an effective, safe, cost-effective method without the need for hospitalization to prepare the cervix in pregnant women.

Keywords

References

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The Iranian Journal of Obstetrics, Gynecology and Infertility
Volume 28, Issue 7
September 2025
Pages 9-20

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