Foley OR MisO for the Management of Induction

Overview

The percentage of women undergoing an induction of labor (IOL) is estimated to be 20% and continues to rise. Simultaneously, the cesarean delivery (CD) rate has continued to increase (2). Induction is a known risk factor for CD. Despite numerous studies evaluating time periods to define a failed IOL, there are no guidelines or accepted definitions of when to call an IOL failed given the incremental gain in vaginal delivery when IOL is prolonged. While decreasing the CD rate is an important primary focus in obstetrics, attention must also be paid to the overall length of labor given that prolonged labor is associated with adverse maternal and neonatal outcomes. Furthermore, a prolonged labor is associated with an increase in direct hospital costs and healthcare utilization. The use of cervical ripening agents, such as vaginal prostaglandin and mechanical dilators, has been demonstrated to reduce labor time and CD rate. In addition to specific individual agents, certain dosing and regimens for IOL and active labor have been compared to evaluate whether a particular dose or regimen can decrease the length of labor and decrease the CD rate. Most of these regimens; however, focus on individual induction agents and few have compared the efficacy of using more than one agent simultaneously. Given the associated risks of prolonged labor and limited data evaluating the use of combined cervical ripening agents, our objective is to evaluate the difference in time to delivery among women who undergo an IOL with four different methods.

Prolonged labor increases the risk of maternal and neonatal morbidity as well as increases healthcare costs. There is limited data evaluating the use of two simultaneous induction agents to decrease the time to delivery. 1. Maternal and neonatal morbidity with prolonged labor The adverse maternal and neonatal morbidity association with prolonged labor has been demonstrated in numerous studies. An increase in maternal risk of post partum hemorrhage and endometritis has been associated with prolonged labor. Cheng et al demonstrated that the risk of post partum hemorrhage and endometritis significantly increased with increasing length of labor. Maghoma et al evaluated the latent phase of labor and found a similar increased risk in endometritis but also noted a significant risk in maternal sepsis with a prolonged latent phase of labor. Neonatal outcomes are similarly improved with a shorter duration of labor. In addition to the risk of chorioamnionitis and decreased 5 minute Apgar score, there is also a significantly increased risk of neonatal intensive care unit admission as well as neonatal sepsis with prolonged labor. 2. Increased healthcare utilization with prolonged labor Both direct and indirect medical costs have been evaluated in the obstetrics literature. A prolonged labor has been associated with an increase in direct and indirect medical costs as well as an increase in healthcare utilization. Mackenzie et al evaluated the cost of different induction regimens and found a decreased cost for women that remained on the antenatal unit for a shorter period of time. 3. Use of simultaneous induction agents Pettker et al evaluated the use of a transcervical foley with and without oxytocin and found no difference in mode of delivery or delivery within 24 hours. They found that labor was 2.5 hours shorter with the addition of oxytocin although the study was not powered to see a statistical difference. Other studies have looked at the concurrent use of prostaglandin with cervical foley. Barrilleaux et al evaluated the use of oral misoprostol with cervical foley compared to cervical foley alone and found no difference in time to delivery; however, the use of oral misprostol has well known side effects, including a high rate of tachysystole which was found in this study. Hill et al reported a decreased time to second stage and time to delivery with the use of cervical foley and oral misoprostol compared to vaginal misoprostol alone; however this was a small study that used with a higher, more favorable starting Bishop score in the combined foley+misoprostol group, biasing them away from the null. Standardized time cut offs during IOL were not used in this study. Recently, Carbone et al performed a randomized trial comparing foley bulb and misprostol to misoprostol alone and found a decreased time to delivery among those in the combined group. This study was a small trial with 60 patients in each arm and did not compare the combined agents to cervical foley alone. 4. Standardization of IOL The optimal length for an IOL is not well established and data on definitions of a failed IOL and prolonged latent phase are lacking. Multiple studies have shown that within 6 hours of oxytocin administration, 60-70% of patients are in active labor. Although data suggest that the longer latent labor is allowed to proceed, the more women that will deliver vaginally, there is also evidence of an increased risk of morbidity, without a large incremental gain. Certain dosing and regimens of individual agents have been evaluated to try and decrease labor; however, studies have not evaluated the use of time cut offs during an IOL to help reduce variation in practice and standardize the IOL process.