A flow diagram of the included and excluded studies is shown in Fig 1. The database searches identified 432 records. After removing the duplicates (n = 137), two reviewers (MM and SF) screened the titles and abstracts for potentially relevant studies (n = 295) independently. Seven full-text RCTs were assessed for eligibility. Three full-text articles excluded due to: one reported non- concurrent administration of oxytocin and Foley catheter, one had a study design not of interest, and the last one was clinical trial registered on clinictrials.gov with no published full text yet. So, four studies were included in the meta-analysis.
Characteristics of studies
The trails included a total of 430 women in the group of Foley catheter plus oxytocin, and 433 in the Misoprostol group that was published between 1999 and 2016. The characteristics of the studies included in the meta-analysis are shown in table 1. Out of the four included studies, three were conducted in USA, (17-19), and one in Nigeria (20). In general, the included participants had singleton pregnancies with an unfavorable cervix, intact membranes, and with the fetus in cephalic presentation in the third trimester of pregnancy. Three studies recruited primi- and multigravida women (17-19). One study enrolled only multigravida women (20). Only in two studies, the main outcomes were reported separately by primi and multigravidas (17, 19).
Risk of bias in included studies
The random sequence and allocation concealment were reasonable in most trials (100% and 60%, respectively). The lack of blinding in most of the study trials was likely to be the main source of bias; only one trial reported an adequate description of blinding of the study subjects (13). Selective reporting was reasonable (60%) but incomplete outcome data was considered a high risk of bias in most of the included trials (Figure 2).
Effects of interventions
Cesarean section rate
A. Foley plus oxytocin vs. vaginal Misoprostol
As indicated in Fig 3, there were 430 participants in Foley plus oxytocin groups and 433 in misoprostol groups. The overall cesarean section rate in Foley plus oxytocin group was not significantly different from Misoprostol groups (OR: 091, 95% CI: 0.71-1.18). Subgroup analysis of primiparous and multiparous women didn’t show any differences in the rate of cesarean section in both groups (OR = 1.00; 95 % CI: 0.63, 1.60, in primiparous vs. OR = 0.68; 95 % CI: 0.33, 1.42 in multiparous).
B. Foley+ oxytocin vs. Foley + vaginal Misoprostol
Only one study compared the cesarean rate between Foley plus oxytocin versus Foley + vaginal Misoprostol (17). The result regarding the cesarean rate was not different between the two groups (OR = 1.14; 95 % CI: 0.66, 1.98). However, in the subgroup analysis of multiparous women vs. primiparous, there was an increased rate of cesarean section in Foley plus oxytocin group in multiparous women.
C. Foley + oxytocin versus oral Misoprostol
In one study cesarean section rate was assessed between Foley plus oxytocin group versus oral Misoprostol. The overall cesarean section rate was not significantly different between the two groups (OR = 0.99; 95 % CI: 0.51, 1.91) (19).
Mean duration of induction to delivery
Three studies (n= 554 women) were included in the meta- analysis of mean duration of induction to delivery in two groups (Fig 4). Foley plus oxytocin decreased the mean duration of induction to delivery compared to vaginal Misoprostol (MD = -6.74; 95% CI -9.20, -4.28) in nuligravidae but not in multigravidae (MD = -0.87; 95% CI -5.09, 3.35). One study compared mean duration from insertion of catheter to delivery between Foley plus oxytocin versus Foley plus vaginal Misoprostol. The overall mean duration in Foley plus oxytocin group was not significantly different from Foley plus vaginal Misoprostol group (MD = 1.08; 95 % CI: -0.78, 2.95) (17).
Delivery in less than 12 hours from induction
As indicated in Fig 5, there were 67 participants in Foley plus oxytocin group and 39 participants in vaginal Misoprostol group. Delivery in less than 12 hours from induction in Foley plus oxytocin group was significantly more than that in the Misoprostol groups (OR = 2.08; 95 % CI: 1.43, 3.02). Subgroup analysis of primiparous women showed significant decrease in the time of delivery in Foley + oxytocin group (OR = 2.21; 95 % CI: 1.18, 4.15) (17,18).
Comparison between Foley plus oxytocin versus Foley plus vaginal Misoprostol showed the overall mean duration in Foley plus oxytocin group was not significantly different from Foley plus vaginal Misoprostol group (OR = 0.85; 95 % CI: [0.51, 1.41], P =0.53). (17).
Two studies with 418 participants reported admission in neonatal intensive care unit (NICU) rate (17, 18). There was no significant difference between Foley plus oxytocin and vaginal Misoprostol groups (OR = 0.72; 95 % CI: 0.0.41, 1.24) (Fig 6).
Two studies (involving 428 women) were included in the meta- analysis of neonatal sepsis (17,18). There was no significant difference between Foley plus oxytocin and vaginal Misoprostol groups (OR = 0.64; 95 % CI: 0.24, 1.75).
Hyper-stimulation or terbutaline use
Two studies (involving 418 women) were included in the meta-analysis for assessment hyper-stimulation or terbutaline use (17,18). There was no significant difference on the rate of hyper-stimulation or terbutaline use between Foley plus oxytocin and vaginal Misoprostol groups (OR = 0. 069; 95 % CI: 0.38, 1.25).
Others adverse outcomes
There was only one study that assessed the rate of chorioamnionitis and endometritis between Foley plus oxytocin and vaginal Misoprostol groups (17). The result of analysis showed significantly higher rate of chorioamnionitis in vaginal Misoprostol group compared to Foley plus oxytocin (OR = 2.35; 95 % CI: 1.02, 5.39). However, there was no significant difference between two groups regarding the rate of endometritis (OR = 1.37; 95 % CI: 0.67, 2.82).