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Table 3 Basic demographic and obstetric variables

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

Variables* Number of studies analysed Interventions Pooled effect (95% CI)x Q p-valuey I2- statisticy p-valuez
Double Single
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 insertionB 4 [15,17,19–20] 337 332 0.02 [−0.19, 0.23] 0.42 0 0.85
Induction indications
 PostdatesC 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
  1. *: Only those variables contained in more than one study are displayed in this analysis table
  2. Only Hoppe 2015 [17] described oligohydramnios and abnormal foetal monitoring and did not reveal significant differences
  3. Rab 2014 [19] mentioned data on body mass index (BMI) at insertion, while Salim, 2011 [20] reported BMI data before pregnancy
  4. Not all of the baseline data was described in Haugland, 2012 [16] and Solt, 2009 [21]
  5. A: Pennell 2009 [18] described the maternal age and gestational weeks by median and typical range. The results remained the same after sensitivity analysis
  6. B: Pennell 2009 [18] described the Bishop score using ordinal data, making synthesis impossible
  7. C: Postdates, as one of the induction indications, shows heterogeneity between the two studies [17, 18]
  8. x: The odds ratio (OR) was the pooled effect for dichotomous variables. The mean difference (MD) was the pooled effect for continuous outcomes
  9. y: Study heterogeneity was explored using Cochrane’s Q test and the I2-statistic test. Random- and fixed-effect models were used as appropriate
  10. 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