Foley Bulb Traction for Cervical Ripening

Over the last 20 years the number of induced labors doubled so that over one in five births in 2003 was induced. In response to the rising need for cervical ripening the American College Obstetricians and Gynecologists have stated that both mechanical and prostaglandin ripening is acceptable and safe.

Prior to beginning an induction, the Bishop score (cervical dilation, effacement, station, consistency, and position) is assessed. With Bishop scores less than five, a cervical ripening agent is commonly used. The mechanical dilation with a foley catheter works by both a direct stretching of the lower uterine segment and cervix and a local inflammatory response that releases matrix metalloproteinases and prostaglandins. It is often chosen due to its lower cost, low incidence of systemic side effects, and low risk of hyperstimulation.

Compared to misoprostol a foley with oxytocin was more effective at induction in primiparous patients, more effective at improving the dilation, safe to use after misoprostol, and not associated with an increased risk of uterine rupture in a vaginal birth after cesarean (VBAC). The foley was also shown to have a shorter induction time and less contractile abnormalities than prostaglandin E2 gel and no increased rate of uterine rupture in VBAC attempts. The use of extra-amniotic saline infusion with a foley catheter has been used to augment the mechanical stretching, however this did not decrease the induction time or improve the outcomes. Finally, a Cochrane Database review found that mechanical methods of cervical ripening were equally effective as prostaglandin agents.

Although the safety, efficacy, and side effects of foley catheter ripening have been compared with multiple other methods for cervical ripening, very few studies have compared different protocols for foley placement. One study showed that the use of oxytocin while the foley catheter was in place did not significantly shorten the time to delivery. Levy et al showed that a larger, 80 ml, balloon resulted in a greater post-ripening dilation and a higher number of deliveries in 24hours. No study to date has examined how the traction placed on the foley catheter affects the outcome.

Therefore, we propose doing a randomized controlled study in which the control is the current standard of care at MetroHealth Medical Center of placing a 500cc weight on the foley and placing it to gravity over the end of the bed. The comparison will be the method used at many institutions where the foley catheter is placed on gentle traction and taped to the inner thigh of the patient.

The primary outcomes measured will be a post-ripening dilation of 3cm or more and time to delivery. The secondary outcomes are patient pain/comfort rating and method of delivery.

Inclusion criteria

• Single viable intrauterine pregnancy
• Cephalic presentation
• Bishop score <6
• Need for induction of labor

Exclusion criteria

• Multiple gestation
• Bishop score >6
• Spontaneous labor/regular contractions on admission
• Rupture of membranes
• Previous uterine scar
• Grandmultiparity (greater than 5 deliveries)