Double- versus single-balloon catheters for labour induction and cervical ripening: a meta-analysis

Table 3 Basic demographic and obstetric variables

Variables*	Number of studies analysed	Interventions		Pooled effect (95% CI)^x	Q p-value^y	I²- statistic^y	p-value^z
Variables*	Number of studies analysed	Double	Single	Pooled effect (95% CI)^x	Q p-value^y	I²- statistic^y	p-value^z
Maternal age (years)^A	5 [15,17–20]	444	442	0.73 [−0.08, 1.53]	0.89	0	0.08
Gestational weeks (weeks)^A	5 [15,17–20]	444	442	−0.07 [− 0.31, 0.17]	0.71	0	0.56
Bishop score at catheter insertion^B	4 [15,17,19–20]	337	332	0.02 [−0.19, 0.23]	0.42	0	0.85
Induction indications
Postdates^C	2 [17–18]	157	158	1.10 [0.51, 2.37]	0.15	51%	0.81
Diabetes mellitus	3 [17–18,20]	305	303	1.35 [0.80, 2.26]	0.20	39%	0.26
Hypertensive disease	3 [17–18,20]	305	303	0.98 [0.66, 1.44]	0.21	35%	0.91
Intrauterine growth restriction	2 [17–18]	157	158	0.92 [0.39, 2.21]	0.23	29%	0.86

*: Only those variables contained in more than one study are displayed in this analysis table
Only Hoppe 2015 [17] described oligohydramnios and abnormal foetal monitoring and did not reveal significant differences
Rab 2014 [19] mentioned data on body mass index (BMI) at insertion, while Salim, 2011 [20] reported BMI data before pregnancy
Not all of the baseline data was described in Haugland, 2012 [16] and Solt, 2009 [21]
A: Pennell 2009 [18] described the maternal age and gestational weeks by median and typical range. The results remained the same after sensitivity analysis
B: Pennell 2009 [18] described the Bishop score using ordinal data, making synthesis impossible
C: Postdates, as one of the induction indications, shows heterogeneity between the two studies [17, 18]
x: The odds ratio (OR) was the pooled effect for dichotomous variables. The mean difference (MD) was the pooled effect for continuous outcomes
y: Study heterogeneity was explored using Cochrane’s Q test and the I²-statistic test. Random- and fixed-effect models were used as appropriate
z: The p-value ≥0.05 for the test indicated that the pooled effect was insignificant; for dichotomous outcomes, the test was OR = 1; for continuous outcomes, the test was MD = 0

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