(192) Labor length differences with 30cc versus 60cc Foley inflation when combination ripening methods are utilized

Data supports shorter time to delivery with 60cc vs. 30cc Foley inflation for labor induction (IOL). Similarly, combination cervical ripening has a shorter time to delivery compared to single-agents. To date, no study has evaluated incremental benefit of higher Foley volume in the setting of combination ripening methods.

Study Design:

This is a secondary analysis of a prospective cohort study evaluating standardized IOL management at 2 sites. Any cervical ripening method could be used. Site#1 used 60cc Foley inflation, while Site#2 used 30cc. For this analysis, patients were included if they underwent a term (≥37 week) IOL from 2020-2022 with a singleton, intact membranes, and received combination methods of Foley and misoprostol or oxytocin. Standardized IOL included regular cervical exams, amniotomy if ≥4cm, and active management of dystocia. 1:1 propensity score matching balanced baseline parameters (age, race/ethnicity, insurance, BMI, parity, and IOL indication). Time-to-event regression analyses for labor length, censored for CD, was modeled with a Cox proportional hazard model. Secondary outcomes included CD and maternal/neonatal morbidity.

Results:

 Of 4295 inductions, 2117 (49.3%) utilized combined cervical ripening methods. After propensity score matching, 1480 were included. Even in the context of combined ripening and standardized IOL, Foley inflation to 60cc was associated with 3-hour shorter labor than 30cc (14.6h[10.4-21.3] v. 17.7h[12.4-24.4], p< 0.001). When censored for CD, patients who received 60cc Foley inflation delivered 70% faster than those who received 30cc (Hazard Ratio, HR 1.73[1.36-2.21]). 60cc inflation was also associated with reduced time to amniotomy (6.6h[4.5-9.8] v. 9.1h[6.4-12.4], p< 0.001). There was no difference in CD (18.9% v. 17.7%, p=0.55), maternal morbidity (15.5% v. 18.0%, p=0.21), or neonatal morbidity (3.4% v. 2.6%, p=0.36).

Conclusion:

Even when using combined cervical ripening methods, 60cc Foley inflation is associated with reduced time to delivery as compared to 30cc without increasing morbidity, and should be considered to optimize labor length.