Background: Missed abortion refers to pregnancy products remain dead with age less than 20 weeks in the womb for several weeks. This study was designed to evaluate the efficacy of castor oil on cervical ripening in the treatment of abortion.

Materials and Methods: This triple blind clinical trial was done on 72 women with missed abortion who were divided into two groups of 36 patients based on odd or even numberd of cases. The case groups received 800 mg vaginal misoprostol and 60 ml castor oil mixed with fruit juice and control groups received 800 mg vaginal misoprostol and 60 ml placebo with fruit juice, respectively. In both groups, if needed, 3 doses of vaginal suppository 800 mg were repeated with at least 24 hours. After the disposal of pregnancy products, sonography and curettage were performed if necessary.

Results: During the intervening period, the time of the opening of the cervix in the intervention group was shorter than control group and there was a statistically significant difference (p=0.032). Also, the control group required a higher frequency of administration of misoprostol than intervention group and the difference was statistically significant (p = 0.037).

Conclusion: It seems that the castor oil can be effective on cervical ripening for treatment of abortion.