Added tension to transcervical catheters does not expedite delivery

1. The application of tension to a transcervical foley catheter for cervical ripening resulted in a significantly faster expulsion of the catheter, but not a shorter total time to delivery.

2. There was no difference in likelihood of vaginal delivery in 24 hours or in rates of cesarean delivery between the 2 groups.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Nearly 1 in 4 deliveries in the United States require induction each year. Inductions typically are performed using an infusion of Pitocin, a drug that mimics the body’s natural hormone oxytocin. Prior to starting Pitocin, however, a woman’s cervix must first be favorable, meaning it is soft, dilated, and effaced enough to be receptive to labor augmentation. Cervical ripening can be achieved either with prostaglandin medications, like misoprostol, or with mechanical methods, such as with transcervical catheter balloons. Catheters are low in cost, quickly removable, and less likely than misoprostol to cause frequent contractions, known as tachysystole. Typically, a Foley catheter is inserted through the cervix and the balloon is inflated in the uterus. It is believed that both the mechanical stretching of the cervix and a release of prostaglandins help encourage cervical change. While a number of recent studies comparing the use of transcervical ripening balloons to other cervical ripening methods have found catheters to be equally effective, the ideal method of catheter use (i.e. inflation volume, type of inflation fluid, and technique), remains controversial. In this randomized controlled trial, researchers looked at whether placing the balloon on tension by taping the catheter to the woman’s leg (a common, but not universal practice) resulted in shorter delivery times compared to a catheter placed without tension.

Results indicated that a Foley catheter with tension led to significantly faster catheter expulsion, but was not linked to a change in time to delivery. Strengths of this study included rigorous randomized design. While there was a trend towards greater likelihood of Cesarean delivery in the non-tension group, the study was not powered to find a difference in this secondary outcome. Moreover, the population was largely homogenous (>70% African American), limiting generalizability to a more diverse population. Larger studies in a more diverse population might reassess this question to clarify whether catheter tension impacts risk for Cesarean delivery.

Click to read the study in American Journal of Obstetrics and Gynecology

Relevant Reading: Induction of labour at term with oral misoprostol versus a Foley catheter (PROBAAT-II)

In-Depth [randomized controlled trial]: Women undergoing cervical ripening were randomized to receive a Foley balloon catheter applied to tension by taping the catheter to the woman’s thigh (n = 67) or to no tension (n = 73). All patients also received low dose oxytocin (max 6 milliunits/min) after Foley catheter placement. The primary outcome was time from catheter insertion to delivery. Secondary outcomes included time from insertion to expulsion, likelihood of delivery within 24 hours, cesarean delivery rate, pain scores, amount of oxytocin infused, and chorioamnionitis.

There was no difference in time from insertion to delivery between the 2 groups (16.2 hours vs. 16.9 hours, p = 0.814), but the median time from catheter insertion to expulsion was shorter in the tension group (2.6 hrs vs. 4.6 hrs, p < 0.001). There was no difference in the likelihood of having a vaginal delivery within 24 hours between the two groups (79% vs. 71%, p = 0.365), nor in cesarean delivery rates (25% vs. 37%, p = 0.139).

Image: CC/Wiki/Olek Ramesz

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