Context: Despite wide use of castor oil to initiate labor, the obstetric literature contains few references to this botanical laxative. Derived from the castor plant Ricinus communis, castor oil may possess properties that are useful in post-term pregnancies.
Objective: To evaluate the relationship between the use of castor oil and the onset of labor.
Design: Prospective evaluation.
Setting: A community hospital in Brooklyn, NY.
Patients: A total of 103 singleton pregnancies with intact membranes at 40 to 42 weeks referred for antepartum testing. Inclusion criteria included cervical examination, Bishop score of 4 or less, and no evidence of regular uterine contractions.
Intervention: Patients were alternately assigned to 1 of 2 study groups: a single oral dose of castor oil (60 mL) or no treatment.
Main outcome measures: Castor oil was considered successful if labor began within 24 hours after dosing. Groups were compared for onset of labor in 24 hours, method of delivery, presence of meconium-stained amniotic fluid, Apgar score, and birth weight.
Results: Fifty-two women received castor oil and 48 were assigned no treatment. Following administration of castor oil, 30 of 52 women (57.7%) began active labor compared to 2 of 48 (4.2%) receiving no treatment. When castor oil was successful, 83.3% (25/30) of the women delivered vaginally.
Conclusions: Women who receive castor oil have an increased likelihood of initiation of labor within 24 hours compared to women who receive no treatment. Castor oil use in pregnancy is underreported worldwide. This small series represents the first attempt to evaluate the medication.