Investigating the effect of Primrose Capsule (Primula Flower Oil) on cervix preparation and commencement of child delivery pains

Investigación del efecto de Primrose Capsule (Primula Flower Oil) en la preparación del cérvix y el comienzo de los dolores de parto infantil

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Delivery induction is one of the common clinical cases with a prevalence rate between 10% and 30%. Cervix readiness is one of the important conditions before delivery induction in such a way that it is estimated that normal delivery does not occur in the absence of ready cervix ¹. The most common method for cervix preparation is Bishop’s scoring system (Bishop Score). The time to vaginal delivery is in an inverse relationship with Bishop’s score. This scoring system includes five items, namely dilation, effacement, fetus head’s position, cervix’s consistency and state. Scores above six indicate the vaginal delivery likelihood and scores below six are reflective of the reduction in the natural delivery success¹.

Various methods have been suggested for cervix preparation. Amongst the nonmedicinal methods, the sexual intercourse, stimulation of nipples, nervous stimulation of the skin, hot water bath, enema, acupuncture, herbal medicines, castor oil, mechanical methods and surgery can be pointed out. There are different drugs for preparing cervix. Amongst the available drugs, as well, prostaglandins, including misoprostol, can be pointed out¹. The use of natural processes during pregnancy is one of the notable issues should be researched further³.The prevalence of using plant byproducts in pregnancy has been estimated up to 55% and this amount depends on the geographical region and ethnic cultures⁴. Based on the estimations in the US, between 45% and 95% of the obstetricians recommend plant-based and natural products during pregnancy. In between, evening primrose, castor oil, black cohosh and blue cohosh are more frequently prescribed⁵.

Evening primrose is one of the most common herbal medicines prescribed for cervix preparation but its effectiveness has not yet been proved. It seems that the use of evening primrose during pregnancy has not been prohibited. In some studies, this oil has been used as a supplement⁶, and it has been stated that it might ease the delivery process for the mothers.

Evening primrose is a biennial and wild plant with yellow flowers that grows in the north and south of the US and Europe. The plant is used for treating systemic diseases caused by inflammation (like atopic dermatitis and rheumatoid arthritis, breast pain, menopausal symptoms and pre-menopausal signs⁷. The oil of this plant is one of the most common herbal medicines used for cervix preparation but its effectiveness is yet to be proved⁸. Primrose capsule contains the oil of evening primrose⁹. And it is made from the seeds of this plant and linoleic acid accounts for the greatest quotient of its ingredients (60-65%).

In the end, according to the studies performed up to now, there is a scarcity of research about the effectiveness of evening primrose oil in delivery induction and, additionally, its vaginal use has not been so far examined. Besides reducing the systemic effects, the vaginal out-patient administering of this drug can induce delivery as a noninvasive, cheap and available method with few side effects. According to the aforementioned materials, the present study deals with the investigation of vaginal administering of this product in cervix preparation in pregnancy termination candidates in their week 37 of gestation.

The present study was carried out on pregnant women in their week 37 of gestation (based on LMP or sonography of the first trimester of pregnancy). These women were pregnancy termination candidates and had referred to the emergency unit of Karaj’s Kamali educational-treatment center during 2019. Sampling was conducted based on convenience method. The study sample volume was computed based on the (formula 1) for comparing two means F:

(1)

With α=0.05 (type I error), β=0.2 (type II error, variance=9 and d=4 based on a review of the related texts. According to this, 80 pregnant women were randomly selected as the case group (group A) and 80 women were randomly selected as control group (group B) by picking previously coded packets and allowed to enter the study after offering a written consent.

The study inclusion criteria were as follows: the generally good status of the mother, absence of any hospitalization indicator except pregnancy termination, Bishop Score below 4 during examination, no need for emergency delivery, mother’s ability of quick presence in the treatment center and the individuals with the foresaid conditions who did not want to participate in the study for any reason were put aside.

After acquiring the mood self-reports, vaginal palpation was carried out and the demographic forms were completed. Sampling was conducted by two obstetricians who had found identical examination results during vaginal palpation. Following the examinations, two soft evening primrose capsules (1000 mg) were placed inside the posterior choledosac of the case group participants and two soft placebo capsules (similar in shape and size to primrose capsules) were placed in the posterior choledosac of the control group participants by the obstetricians and the participants were asked to leave a contact number for future follow-ups in regard of the commencement of the delivery pains and delivery time. The collected information was analyzed using Chi-square and t-tests in SPSS. To render the study blond, the obstetricians and the patients as well as the statistical analysts were kept unware of the placebo or drug application on the participants.

Results: Based on the performed studies, the two groups were found not significantly different in terms of mother’s age (P\0.589), number of pregnancies (P=0.905), number of deliveries (P=0.898), infant’s weight (P=0.989) and Bishop Score 9P=0.996), gestation age (P=0.332), education level (P=0.744), first minute Apgar (P=0.941), infant’s gender (P=0.800) and background diseases (P=0.440). These findings can be seen in (Table 1).

The study findings are indicative of the idea that the participants did not significantly differ in terms of T1 (the interval between primrose use and delivery pain commencement) and T2 (the interval between primrose use till delivery). Furthermore, 79 individuals from the case group and 80 individuals in the evidence group were found with no background diseases. Also, no significant difference was documented between the groups’ participants in terms of background diseases in Fisher’s test (P=0.440).

Table 1:
demographic information of the two groups

The mean time spans between capsule use till pain initiation (T1) are 19.06 and 13.4 hours in the case evidence groups, respectively, and the mean time intervals between the capsule use till delivery (T2) are 73.83 and 60.68 hours, respectively (table 2). Based on Fisher’s exact test, there was found no significant difference between T1 in the case group and T2 in the control group (P=0.168). In addition, no significant difference was evidenced between the case and control groups’ participants in terms of T2 (P=0.150).

Table 2:
Comparison between onset of contractions and delivery in two groups

The present study is a clinical case-evidence double blind research conducted on 162 individuals qualified for entering the study (80 individuals in intervention group and 82 individuals in the control group). The study goal was investigating the effectiveness of evening primrose capsule in cervix preparation and initiation of delivery pains. In the present study, the two groups were rendered identical in terms of the fetal variables, mother’s age, and the mother’s BMI, fetus weight, number of pregnancies and number of deliveries as well as education level, score, Bishop Score and fetal gender and the influential background diseases.

Behrashi his colleague showed that numerous factors such as fetus weight at birth and optimality of cervix status influence labor induction¹⁰. In the study by Dove et al and Jahdi and others, as well, the basic information was similar to the present study’s data and the homogenization was conducted for the purpose of increasing the generalization power¹². In various studies, paradoxical results have been reported for the use of medicinal herbs and induction success. In the study by Gholami et al, the initiation time of the delivery signs in the group that had received capsules containing chamomile was significantly lower than the group treated with drugs; additionally, delivery signs were recorded in a larger number of the case group’s participants within a week following the initiation of chamomile capsule use¹³.

In the study by Mohammadini et al, no significant difference was observed between the group treated with hedge-mustard seeds and the control group in terms of the spontaneous commencement of the delivery pains¹⁴. Moreover, in the study by Turk Zahrani, receiving wild rue smoke twice a day significantly increased cervix preparation and the results were found indicating a significant difference in terms of the delivery initiation time and the duration of the first and the second stages of delivery between the intervention and control groups¹⁵. There is a scarcity of research on the present study’s goal and none of the studies have dealt with the vaginal use of this oil for softening the cervix for advancing the labor¹⁶. In another study, Bishop Score’s variations were found significantly larger in the intervention group treated with evening primrose oil than the control group¹⁷.

Evening primrose oil features prostaglandin effects¹¹. The most important components of the oil are linoleic acid and gamma-linoleic acid that is a natural precursor of prostaglandins¹⁸.

Various studies showed that the use of evening primrose causes significant increase in gamma linoleic acid in the blood¹⁹.

Due to prostaglandin properties of evening primrose oil that is used in line with preparing cervix and initiation of delivery pain, the study that was conducted for investigating the effect of oral use of western primula on Bishop Score and cervix length in Filipino women, a significant relationship was found between the intervention and control groups’ participants in terms of the changes in Bishop Score and cervix length²⁰.

Furthermore, in the study by Vahdat et al who investigated the effect of western primula flower’s oil on the softening of cervix in hysteroscopy candidates with no past record of normal delivery²¹, the total time of the cervix dilation duration was shorter²². The aforesaid studies’ results are consistent with the present research’s findings.

In the study by Jahdi et al, the difference in Bishop Score was not significant between the intervention and control groups²³. In the study by Bazrafcan et al who examined the effect of the oral use of primula flower oil on the pregnancy duration and gestation outcomes, no significant difference was observed between the intervention and control groups’ participants. The results of the two foresaid studies are consistent with the present research’s findings⁹.

The reason for the paradoxical results in various studies might be the differences in the intervention type, study method and sampling styles. In the current research paper, no side effect of using evening primrose ointment was evidenced. In the study by Esmaeilzadeh et al, as well, the use of evening primrose was found accompanied by such side effects as extreme increase in uterus contractions and the subsequent increase in the risk of the membrane rupture. The reason for this problem could be the use of higher dosages for longer periods of time. So, according to the study constraints regarding the amount and the duration of ointment use as well as considering the scarcity of the studies conducted in this regard and also bearing witness to the paradoxical results of the various studies, doing further research including comparative examinations using various plants and herbs is recommended.

Acknowledgement: Researcher apperciated clinical research development center of Kamali hospital in Alborz University of medical science.