The effect of evening primrose and castor oil capsule on Bishop Score and some delivery outcomes (triple-blind clinical trial)

In several studies, the effect of evening primrose and castor oil on bishop score and delivery outcomes have been investigated, but comparing their effects is questionable. This study was performed with aim to compare the effect of oral castor oil and evening primrose at the same time with induction of labor on Bishop score and some delivery outcomes in pregnant women.

This triple-blind randomized clinical trial study was performed in 2019 on 114 pregnant women referring to Niknafs maternity hospital of Rafsanjan. The subjects were randomly divided into two intervention group. The first intervention group received two capsules of 1000 mg of evening primrose and the second received 6 capsules of castor oil concurrently with labor induction. Bishop's score information and delivery outcomes were collected using the hospital records. Data were analyzed by SPSS software (version 16) and analysis of variance in repeated measures, Chi-square, and independent t-tests. P<0.05 was considered statistically significant.

The mean and standard deviation of evening primrose and castor oil in each group were effective on the bishop score two hours after induction (5.02 ± 1.42, 5.36 ± 1.69, respectively) (P=0.542) and four hours after induction (7.32 ± 1.94, 7.63 ± 1.58, respectively) (P=0.492) and the difference was statistically significant. Comparison of mean differences within each group of evening primrose capsules and castor oil was significant (P<0.001). There was no statistically significant difference between the two groups in terms of bishop score, type of delivery, Apgar score, first and fifth minutes, length of first and second stage of labor (P>0.05).

There was no statistically significant difference between evening primrose and castor oil on cervical ripening and pregnancy outcomes at the same time as labor induction, therefore, the use of one is not superior to the other.