Conventional versus modified application of COOK Cervical Ripening Balloon for induction of labor at term: a randomized controlled trial

Abstract

Background This study aims to evaluate the efficacy and safety of the modified application of COOK Cervical Ripening Balloon (CCRB) for induction of labor (IOL) at term in primipara. Methods A total of 227 singleton full-term pregnancies with indications of IOL were enrolled and randomly divided into the control and study groups in our hospital from January 2021 to December 2021. In the control group, a conventional method was used. Both the uterine and vaginal balloons were filled to 80 mL and removed after 12 hours. In the study group, a modified method was used. The uterine and vaginal balloons were filled to 120 mL and 40 mL respectively. Small weight traction was given to help CCRB discharged after 12 hours placement. Oxytocin was administered in both groups after CCRB was discharged without labor starting. The improved Bishop scores, duration of labor, and spontaneous delivery rate were evaluated in the two groups. Results The improved Bishop scores in the study group were 3.06 ± 0.97 at 12 hours placement of CCRB and 4.37 ± 0.87 when CCRB was discharged, which were significantly higher than 2.52 ± 0.79 in the control group (p < 0.05). The first and total stages of labor in the study group were significantly shorter than those in the control group ((6.17 ± 2.85) h vs. (7.27 ± 2.90) h, p = 0.010; (7.07 ± 3.18) h vs. (8.09 ± 3.11) h, p = 0.028). No difference in spontaneous delivery rate between the two groups was observed. But the delivery rate within 24h between the two groups had a significant difference (79.79% vs. 55.91%, p < 0.05). For the cases with initial Bishop scores ≤ 3, the improved score was significantly increased, the first and total stages of labor were significantly shorter in the study group than those in the control group (p < 0.05). Those