Post-term pregnancies are pregnancies that last more than 42 full weeks (294 days) from the first day of the last menstrual period. With increasing gestational age, the rate of maternal and fetal morbidity and mortality significantly increases. Among medical methods, misoprostol is widely used to prepare the cervix in post-term pregnancies. But today, due to the high side effects of misoprostol, especially the increasing need for cesarean section, some complementary medicine methods are used to prepare the cervix. The aim of this study was to compare the effect of Misoprostol and Evening primrose oil capsule with Misoprostol on delivery method in post-term pregnancies. 

 

This study was performed as a single-blind randomized clinical trial on 130 pregnant women with post-term pregnancy referring to the delivery ward of Besat Hospital in Sanandaj, Iran. The samples were selected by available sampling method and assigned to the intervention and control groups by random sampling method. In the intervention group, a 500 mg capsule of evening primrose oil was given vaginally and 25 micrograms of misoprostol were given sublingually, and in the control group, an ineffective capsule was given vaginally with 25 micrograms of misoprostol sublingually. Demographic data, clinical characteristics and delivery method were used for data collection. Data were analyzed by SPSS software version 21 (SPSS Inc., Chicago, Ill., USA) and statistical tests such as Chi-square, t-test, and ANOVA. A P-value less than 0.05 was considered significant.

The aim of this study was to compare the effect of misoprostol and vaginal capsule of evening primrose oil with misoprostol in cervical care in terms of the type of delivery in postmenopausal women admitted to the maternity ward of Besat Hospital in Sanandaj. Based on the statistical analysis of the data, there was no significant difference between the two groups in terms of demographic characteristics (age, education, occupation and place of residence) and obstetric characteristics (gestational age, history of abortion, history of curettage and estimated fetal weight). These points were quite homogeneous; therefore, by matching these variables with more confidence, the obtained results can be considered as a result of the effect of the implemented intervention and the results will have more generality. Regarding the Bishop score, there was no significant difference between the two groups before the intervention (P value = 0.73). Still, after the evening primrose oil and misoprostol groups intervention, the mean Bishop score increased significantly compared to the placebo and misoprostol groups (P value<0.05). In this regard, in the study of Tahermanesh et al. (2015), which aimed to investigate the effect of evening primrose oil on cervical care and cervical dilatation before hysteroscopy, it was reported that evening primrose oil capsules are effective in cervical care [17]. In a study by Shahali et al., which aimed to investigate the effect of vaginal consumption of evening primrose oil on cervical preparation in primiparous women with late term pregnancy, it was found that vaginal administration of evening primrose oil reduced the duration of the latent stage and had a positive effect on softening the cervix [2]. Also, in the quasi-experimental study of Dianso et al., which was performed on the effectiveness of evening primrose oil on cervical preparation, the changes in Bishop score in the intervention group were significantly greater, and in 85% of the intervention group, the Bishop score improved [23].
The results of these three studies are in line with the results of the current study and indicate the effect of evening primrose oil on cervical maturation. Also, this drug is easy to use, available and cheap and has no significant side effects. In the present study, a significant increase was observed in the Bishop scores of the participants in the evening primrose and misoprostol groups compared to the placebo and misoprostol groups, which indicates the effectiveness of this drug in cervical care.
On the other hand, in the study of Jahdi et al., which was performed on the effect of oral capsules of evening primrose oil on cervical care in nulliparous pregnant women, the results showed that oral capsules of evening primrose oil were used orally in pregnant women with gestational age (40 weeks to 40 weeks and 6 days) does not cause much change in Bishop score for a week [16]. In a previous study by Dove and Johnson, it was reported that oral consumption of evening primrose oil from 37 weeks of gestation until delivery not only reduces pregnancy length and libido but also slightly increases the incidence of long-term rupture of fetal membranes, strengthens uterine contractions, stops the fetal decline and leads to the use of vacuum [21].
 Regarding the side effects and type of delivery performed in the study of Abedi Asl et al., which aimed to compare the effect of vaginal misoprostol and intracervical follicle catheter on cervical preparation before delivery, it was reported that the total time from induction to labor was similar in both groups [24]. Also, in the study of Alinejati et al., who compared the efficacy and side effects of trans cervical catheter and vaginal misoprostol on cervical preparation, tachysystole was more significantly observed in the misoprostol group. Therefore, it has been suggested that misoprostol should be limited in cases where the risk of tachycardia systole is higher (for example, in cases with increased risk of fetal hypoxemia including intrauterine growth restriction, oligohydramnios, post-term pregnancy, thrombosis, Preeclampsia) [14].
In the present study, the results indicate that the rate of cesarean section in placebo and misoprostol groups was higher than that in evening primrose oil and misoprostol groups due to the use of high doses of misoprostol and impaired fetal heart rate, excretion, and aspiration of meconium. 

 

The results of the study showed that the use of vaginal capsules of evening primrose oil with misoprostol compared to misoprostol alone while helping to ripen the cervix is associated with a lower rate of cesarean section. 

 

This article is the results of the master's thesis of Kurdistan University of Medical Sciences. This article was registered in the Clinical Trial Registration Center with the code (IRCT20180224038846N1) and in the ethics committee with the code ir.muk.rec.1396/36. The authors at this moment express their appreciation and gratitude to the project partners, dear mothers, staff of the Student Research Center, and members of the Research Council of Kurdistan University of Medical Sciences who cooperated sincerely in approving and implementing this project.

 

The authors declared no conflict of interest.