Double-balloon catheter results in higher rate of vaginal delivery within 24 h when compared with dinoprostone vaginal insert
- Correspondence to: Anthony C Sciscione
Christiana Care 4755 Ogletown Stanton Road, Suite 1905, Newark, DE 19718, USA
Commentary on: Google Scholar
Induction of labour is one of the most common obstetric interventions. In 2006, 22.5% of all the births in USA were as a result of labour induction.1 The mechanisms for induction of labour are generally divided into two categories: mechanical (intracervical catheter, laminaria, extra-amniotic saline infusion) and pharmacological (progesterones and oxytocin). Both methods employ prostaglandins (excluding oxytocin) to promote cervical ripening; mechanical methods cause physical dilation of the cervix and increase the release of endogenous prostaglandins while pharmacological methods involve oral or vaginal administration of exogenous prostaglandins. Two of the most common induction methods, misoprostol and the Foley catheter are used ‘off label’. The authors of this study chose to compare the two products specifically designed for cervical ripening during the induction of labour: the double-balloon intracervical catheter versus the PGE2 vaginal insert.
Although there are numerous studies comparing various induction mechanisms, there is little continuity in protocols or outcomes of interest. Cromi and colleagues chose vaginal delivery within 24 h as their primary outcome. This parameter was established based on recommendations by WHO, NICE and the Cochrane Collaboration that ‘vaginal delivery within 24 h’ is the most ‘clinically relevant measure of effectiveness for trials of methods of labour induction’.
The authors powered their study to detect a 20% increase in vaginal delivery within 24 h when the double-balloon catheter was utilised. The study group had 105 women in each treatment arm. All the women who presented to the hospital for a scheduled induction of labour at ≥ 34 weeks gestational age, with a Bishop's score ≤ 6, were randomised to either receive a double-balloon catheter or the PGE2 vaginal insert. By comparing the two methods specifically produced for the induction of labour, the protocols for each method were based on manufacturer recommendations for use. Once the device, catheter or insert, was expelled or removed, amniotomy and oxytocin was used to further augment labour as per institution standard protocol.
Secondary outcomes analysed included caesarean delivery rate, improvement in Bishop score after ripening, ripening-to-delivery interval, oxytocin administration, epidural request and neonatal outcomes (apgar ≤7 at 5 min, umbilical cord pH < 7.0 and admission to NICU). However, the study was not powered to detect significance in any of the secondary outcomes. Analysis involved the use of the Student's t test and the Mann–Whitney U test to compare continuous variables. The x2 test was used to analyse proportions and a Kaplan-Meier survival curve was created to analyse the proportion of women who did not deliver over time.
There were no significant differences between the demographics of the two treatment groups with each group consisting of approximately 75% nulliparous individuals, an average gestational age of 40.5 weeks and postdates being the most common indication for induction. The double-balloon catheter resulted in a statistically significant increase in vaginal delivery within 24 h compared with that due to the PGE2 vaginal insert (OR 2.22, 95% CI 1.26 to 3.91). Women who received the double-balloon catheter also had a higher rate of oxytocin administration (85.7% catheter vs 54.4%, p<0.0001) and the use of epidural (82.9% catheter vs 61.2% PGE2, p=0.0006). There was no significant difference in the rate of Caesarean delivery, time to the onset of active labour, time to delivery or any of the adverse neonatal outcomes.
The results of this trial demonstrated no difference between the two methods for time from the induction to delivery, but a higher rate of vaginal delivery within a 24 h period for women receiving the intracervical catheter. While not powered to detect adverse outcomes, the results of the study were consistent with the previous literature demonstrating that women who received prostaglandins for labour induction were more likely to experience tachysystole (OR=22.76, 95% CI 1.31 to 3.91). The Cook double-balloon intracervical catheter used in this study provided a higher rate of vaginal deliveries within 24 h, likely increasing patient satisfaction and was significantly less expensive ($41 vs $175) than the prostaglandin intravaginal insert. However, a recent randomised trial of the Foley catheter versus the Cook double-balloon intracervical catheter by Salim et al2 found that women who received the Foley catheter for preinduction cervical ripening were more likely to have a spontaneous vaginal delivery and had less-composite adverse outcomes, and it was significantly less expensive ($0.60 vs $37 ). Mechanical methods appear to be as efficacious and are associated with less adverse events than prostaglandin preparations, which make them an ideal choice for preinduction cervical ripening; the intracervical Foley catheter, owing to the significant cost savings and efficacy, should remain the primary method for preinduction cervical ripening.