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Table 4 Secondary outcomes

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

Outcomes Number of studies analysed Interventions Effect measure Pooled effect (95% CI) Q p-value I2- statistic p-value Sensitivity analysis
Double Single
placement difficulty/failure 4 [15–16,18,20] 382 384 RR 1.34 [0.66, 2.71] 0.55 0 0.42 stable
spontaneous expulsion 4 [15,17,19–20] 337 332 RR 0.86 [0.60, 1.23] 0.0002 85% 0.40 stable
insertion to delivery intervalA 6 [15–20] 532 532 MD 0.98 [− 0.03, 2.00] 0.16 36% 0.06 Unstable I
1.36 [−0.63, 3.34] 0.02 61% 0.18 Unstable II
insertion to expulsion/removal intervalB 4 [15,17,19–20] 278 267 MD 1.72 [−0.35, 3.79] < 0.00001 93% 0.10 Unstable III
expulsion to delivery interval 2 [19,21] 145 150 MD −2.81 [−10.82, 5.19] 0.06 72% 0.49
Bishop score incrementC 5 [15,17,19–21] 382 382 MD 0.57 [0.28, 0.86] 0.30 18% 0.0001 stable
vaginal delivery within 24 h 3 [17–18,20] 305 303 RR 0.95 [0.72, 1.26] 0.11 54% 0.74 Unstable IV
normal vaginal deliveryD 6 [15–20] 532 532 RR 1.02 [0.86, 1.20] 0.03 59% 0.84 Unstable V
assisted vaginal deliveryD 4 [16,18–20] 443 445 RR 1.08 [0.84, 1.41] 0.48 0 0.54 stable
analgesia usage 4 [17–20] 405 403 RR 1.07 [0.99, 1.16] 0.72 0 0.10 stable
maternal adverse events
 maternal infection 5 [17–21] 450 453 RR 1.04 [0.66, 1.66] 0.38 5% 0.85 stable
 postpartum haemorrhage 3 [15,18–19] 246 249 RR 1.03 [0.74, 1.42] 0.73 0 0.88 stable
neonatal adverse events
 low Apgar score (< 7 at 5 min)E 3 [17–18,20] 305 303 RR 0.53 [0.15, 1.88] 0.46 0 0.32
 NICU admission 3 [17–18,20] 305 303 RR 0.70 [0.45, 1.07 0.90 0 0.10 stable
length of hospitalisation 2 [19–20] 248 245 MD 0.16 [−0.10, 0.41] 0.28 15% 0.22
satisfactionF
 pain during the process 2 [15,19] 139 139 MD 0.07 [−0.53, 0.67] 0.42 0 0.82
 maternal total satisfaction 2 [15,19] 139 139 MD −0.10 [−1.25, 1.04] 0.08 68% 0.86
  1. A: No studies, except for those of Hoppe 2015 [17] and Salim 2011 [20], specifically defined delivery as being either total delivery or vaginal delivery. Hoppe 2015 [17] offered data on the time from insertion to vaginal delivery, while Salim 2011 [20] reported both measurements. We synthesised these data by involving Hoppe 2015 [17]. The upper and lower data shows the effects when we added the total and vaginal delivery data from Salim 2011 [20]
  2. B: Salim 2011 [20] excluded 124 women (70 in the double-balloon catheter group and 54 in the single-balloon catheter group) with spontaneous expulsion during this process
  3. C: We depended primarily on the Bishop score increment. For those studies that included only a second Bishop score, we included these data and conducted sensitivity analyses
  4. D: Hoppe 2015 [17] reported only vaginal deliveries but did not define whether assisted vaginal deliveries were included; we treated these data as though it did not include assisted vaginal deliveries
  5. E: Salim 2011 [20] reported no events on this outcome for either arm, which was inestimable
  6. F: All measured by VAS
  7. I: When we eliminated Salim 2011 [20], the MD pooled effect changed to 2.16 [0.76, 3.57] (p-value, 0.003), in favour of the single-balloon catheter. The results remained comparable after all other sensitivity analyses were performed
  8. II: Excluding Rab 2014 [19], though heterogeneity disappeared, the effect remained comparable (Q p-value, 0.17; I2, 38%; p-value, 0.58). Excluding Salim 2011 [20], the result was shown in superscript note I
  9. III: Significant heterogeneity existed regardless of which study we excluded; however, when we repeated the analysis after excluding Salim 2011 [20], the result changed (MD, 2.40 [0.32, 4.48]; supporting the single-balloon catheter)
  10. IV: Stable effect but became homogeneous only when we excluded Hoppe 2015 [17]
  11. V: Stable effect but became homogeneous only when we excluded Rab 2014 [19] or Salim, 2011 [20]