Authors (including presenting author) :
Law BMC(1), Hui PW(1)
Affiliation :
(1)Department of Obstetrics and Gynaecology, QMH
Introduction :
Cervical priming is required before induction of labour (IOL) if the cervix is unfavourable. The assessment is based on the modified Bishop’s score (BS) and a score 7 or more predicts a higher likelihood of vaginal delivery.
Priming can be done mechanically with Cook® cervical ripening balloon (Cook’s balloon) or pharmacologically with prostaglandin E2. The cervical priming balloon is placed through the endocervical canal for 12 hours followed by artificial rupture of membranes (AROM) and syntocinon infusion. For patients receiving pharmacological priming, prostaglandin E2 pessary is placed vaginally for around 24 hours and cervix is reassessed the next day. Caesarean section (CS) would be performed for failed induction if cervix remains tubular after 12 hours.
Objectives :
The primary outcome is the CS rate for failed IOL after use of Cook’s balloon. The secondary outcomes are maternal and neonatal morbidities after use of Cook’s balloon.
Methodology :
It is a retrospective study on patients with singleton term pregnancy, cephalic presenting fetus, intact membranes, unfavourable cervix, with no prior CS, who received cervical priming with Cook’s balloon, from 22 October to 28 December 2024.
Result & Outcome :
A cohort of 54 patients was included. Overall, 29 patients (53.7%) delivered vaginally, including all 10 multiparous patients; 19 patients (35.2%) delivered by CS for failed IOL; and 6 patients (11.1%) delivered by CS for abnormal cardiotocography.
The cervix of 33 patients (61.1%) became favourable after use of balloon and rupture of membranes were feasible in the remaining 21 patients (38.9%) with BS < 7. Failed IOL rate was significantly lower (6/33; 18.1%) in women with favourable cervix compared to patients (13/21; 61.9%) with unfavourable cervix (p< 0.05).
Among patients who had Cook’s balloon as the only cervical priming method, the CS rate for failed IOL was 38.2% (13 out of 34), compared with that of 30% (6 out of 20) in patients who had pharmacological priming prior to insertion of Cook’s balloon (p=0.71).
There was no uterine hyperstimulation and no abnormal fetal heart pattern during cervical priming with Cook’s balloon.
In conclusion, failed induction rate is much lower for patients with favourable cervix after cervical balloon priming, irrespective of whether previous pharmacological method was used. AROM is feasible in all patients after cervical balloon priming but Bishop’s score remains the key determining factor for successful vaginal delivery.
