Induction of labor is a common obstetrical practice. In fact, the rate of induction has risen to 184/1000 live births. It is well known that a favorable Bishop score, defined as Bishop score 5-8, improves the safety and success rate for induction of labor and vaginal delivery. Several methods for cervical ripening, both mechanical and pharmacological, have been developed to improve Bishop score in women eligible for induction of labor with an unfavorable cervix. These methods include: misoprostol, dinoprostone, intracervical catheter with and without extra-amniotic saline infusion, and laminaria.
Several studies have investigated the optimum cervical ripening agent, and review of current literature supports that misoprostol given in a dose of 25 micrograms every 4 hours intravaginally as the most efficacious and inexpensive regimen while maintaining safe maternal and fetal outcomes. Several studies have shown that misoprostol has a significantly shorter time to delivery compared with other methods of ripening. In fact, in a 2003 Cochrane Database Systematic Review, misoprostol was shown to have increased cervical ripening effectiveness and reduced failure to achieve vaginal delivery in 12-24 hours. Further, while uterine hyper-stimulation and tachysystole were more common in the misoprostol groups, no adverse neonatal outcomes were described. However, misoprostol has been shown to have a higher incidence of cesarean section for fetal intolerance to labor compared to other cervical ripening methods including EASI. Several studies support the ideal route of administration and dosage of misoprostol to be 25 micrograms every 4 hours intravaginally. This regimen leads to effective cervical ripening while reducing the dose-dependent effect of misoprostol on uterine tachysystole and hyperstimulation. Another aspect to consider in cervical ripening method is cost. Misoprostol is much less expensive than other methods including dinoprostone. In fact, one article reports that the average cost per patient for misoprostol treatment was $85 compared to $606 for dinoprostone insert.
Extra-amniotic saline infusion (EASI) has been introduced as a mechanical, non-pharmacological cervical ripening method. It involves placement of a Foley catheter through the cervix and is supplemented with continuous extra-amniotic infusion of saline. This is thought to improve prostaglandin release, resulting in shortened duration of labor. Several studies have been performed to determine the safety and efficacy of the EASI method.
Since misoprostol is efficacious, safe, and inexpensive, it is a superior method for cervical ripening and will act as a control for an experimental group undergoing cervical ripening with the EASI catheter. Our hypothesis is that cervical ripening with the EASI method will result in fewer cesarean sections for fetal intolerance to labor as compared to misoprostol. Furthermore, patients undergoing cervical ripening with EASI will experience a shorter time to delivery, have less expense, have fewer adverse effects, and will be more satisfied with EASI catheter than with misoprostol.
