Table 1.

Characteristics of studies included in this meta-analysis

First author’s surname	Year	Type of study	Age: year	Gestational age	Total no=test and control (n)	Pregnancy	IOL in test group n(%)	IOL* in control group n(%)	Significant complications/safety	Explanations and/or other outcomes
Azhari et al.[25]	2006	RCT**	19-35	40-42 weeks	47=24 and 23	Term/singleton	13/24 (54.20%)	1/23 (4.30%)	Nausea was 48% in castor oil group vs 0% in control group	The mean bishop score in the castor oil group increased from 2.50±1.29 to 6.79±3.20 [p<0.001]. The differences in terms of 5 min Apgar score, neonate birth weight, meconium amniotic fluid staining was not significant between control and castor oil groups
Boel et al.[8]	2009	retrospective cohort (history cohort)	28±7	40-41 weeks	384=43 and 341	Term	8/43 (27.90%)	68/341 (41.60%)	No	No evidence for harm of castor oil on mother or baby and also no beneficial effect of castor oil on mother or baby was seen
Davis[13]	1984	Retrospective cohort (history cohort)	28.60	37-42 weeks	196=107 & 89	Term/singleton	80/107 (75%)	52/89 (58%)	No	The effect of castor oil was more pronounced in primiparas; 75% in castor oil vs 54% in control groups. Caesarean incidence was three times in control vs castor oil group (p<0.001)
Gilad et al.[26]	2018	Prospective, randomized, double-blind, placebo-controlled clinical trial	29±5	40-42 weeks	81=38 and 43	low-risk/post-date singleton	20/38 (52.60%)	17/43 (39.50%)	Bowel movement-no serious adverse effect	There were no differences in terms of rates of meconium staining of amniotic fluid, abnormal fetal heart rate tracing, cesarian section and instrumental deliveries, 5 min Apgar score, and the rate of chorio amnionitis, hypertensive complications of pregnancy, retained placenta and PPH between groups. Castor oil is effective for labor induction, in post-date multiparous women but not in primiparous women
Garry et al.[7]	2000	RCT	24.80±6.70	40-42 weeks	100=52 and 48	Term/singleton	30/52 (57.70%)	2/48 (4.20%)	No	5-min Apgar score, neonate birth weight, meconium amniotic fluid staining was same between control and intervention groups
Okoro et al.[28]	2019	RCT	28.7±3.9	40-41 weeks	211=105 and 106		51/105 (48.6%)	23/106 (21.70%)	No	Complications were also similar in the two groups and were mainly “presumed” fetal distress, prolonged labor, maternal exhaustion and prolonged second stage labor
Neri et al.[15]	2018	Retrospective observational case-control study	32.8±4.7	40-41 weeks	80=40 and 40	singleton/low-risk	19/40 (47.50%)	3/40 (7.50%)	Mild nausea and diarrhoea which treated with common medicaments, no need for special care	Women in castor oil group showed a higher incidence of vaginal delivery and lower caesarean rate but the difference was not statistically significance
Saberi et al.[30]	2008	RCT	26.4±4.93	40-42 weeks	200=100 and 100	Term/singleton	70/100 (70%)	30/100 (30%)	No	5-min Apgar score, neonate birth weight, meconium amniotic fluid staining was same between control and intervention groups
Kahnamoyiagdam et al.[14]	2014	RCT	22.64	41 week	100=50 & 50	Term/singleton	29/50 (58%)	21/50 (42%)	No	Caesarean rate was lower in castor oil group (36%) vs control (44%) but it was not significant
Pirdadeh Beiranvand et al.[29]	2007	RCT	25.4±4.4	40-42 weeks	47=24 and 23	Term/primigravida	13/24 (54.20%)	1/23 (4%)	No	The mean Bishop score in the castor oil group increased from 2.50±1.29 (at first) to 6.79±3.20 (at the end) (p<0.001)
Montazeri et al.[27]	2010	RCT		40-42 weeks	80=40 and 40	Term/singleton	25/40 (62.50%)	3/40 (7.50%)	No	5-min Apgar score, neonate birth weight, meconium amniotic fluid staining was same between control and intervention groups
Iravani et al.[31]	2006	RCT			80=40 and 40	post-term/singleton	25/40 (62.50%)	3/40 (7.50%)	No	5-min Apgar score, neonate birth weight, meconium amniotic fluid staining was same between control and intervention groups

*Induction of Labour, **Randomized Clinical Trials