Induction of Labor
– Administration of oxytocin is probably the most common method of labor induction after a ripening process of unfavorable cervices.
Bishop Score (See the table down)
– A score ≥8 suggests the chances of having a vaginal delivery are good and the cervix is considered favorable or ripe for induction. If the Bishop score is ≤6, the chances of having a vaginal delivery are low, and the cervix is considered unfavorable or unripe for induction.
A simplified Bishop score can be calculated using only dilation, station, and effacement.
Using these 3 variables, a simplified Bishop score ≥5 has a similar predictive value for vaginal delivery as a classic Bishop score ≥8.
– Based on the simplified Bishop score, you can start induction by oxytocin if the V/E findings are cx dilation 3-4 cm, 60-70% effaced & -2 station, Not before these findings.
Comparison of drugs used in Induction of Labor :
A network meta-analysis comparing the use of misoprostol, dinoprostone& Foley catheter for cervical ripening concluded that no method was clearly superior when the rates of failure to achieve vaginal delivery within 24 hours, uterine hyperstimulation with FHR changes & cesarean delivery were all taken into account.
1. Vaginal misoprostol followed by vaginal dinoprostone were the most effective methods for achieving delivery within 24 hours; however, these methods had the highest rates of uterine hyperstimulation with adverse FHR changes.
2. The Foley catheter was the least effective method for achieving delivery within 24 hours, but had the lowest incidence of uterine hyperstimulation with FHR changes.
3. Oral misoprostol was the best method for reducing the risk of cesarean delivery and caused less uterine hyperstimulation with FHR changes than vaginal misoprostol.
4. The author’s preference is to use vaginal PGE1 (misoprostol).
– Prostaglandins are not used for cervical ripening or labor induction in term pregnancies with a prior cesarean birth or other prior major uterine surgeries (eg, extensive myomectomies and hysterotomies) because of the increased risk for uterine rupture.
Dosing of drugs used in Induction of Labor :
1. Misoprostol (Cytotec) is a prostaglandin E1 analog available as 200 mcg tablets, which can be broken to provide 25 mcg (the same dose of vagiprost tablet). We administer 25
mcg every 3-4 hours. The WHO suggests 25 mcg every 6 hours. Oxytocin can be
initiated, if necessary, 4 hours after the final misoprostol dose.
2. Prostin E2 gel or tablets (3 mg dinoprostone) are PG E2 analogs.
Cervidil is a vaginal insert containing 10 mg of dinoprostone in a timed-release
formulation (the medication is released at 0.3 mg/h). The insert is left in place until active labor begins, or for 12 hours. Oxytocin can be initiated anytime beyond 30 minutes after removal of the insert. An advantage of the vaginal insert over the gel formulation is that the vaginal insert can be removed in cases of uterine tachysystole or abnormalities of the fetal heart rate tracing.
– A workshop convened by the NICHHD & ACOG proposed that failed induction is
defined as failure to generate regular contractions approximately every 3 minutes and cervical change after at least 24 hours of “oxytocin” administration. Membranes should
be artificially ruptured. After rupture of membranes, the induction may be considered failed if regular contractions and cervical change do not occur after at least 12 hours of oxytocin administration. The workshop’s goal was to provide evidenced-based criteria for reducing the number of CS performed for failed induction in the latent phase of labor. By
allowing the latent phase to extend for 24 hours or more and administering oxytocin for 12-18 hours after membrane rupture, many of these cesarean deliveries can be avoided.
– The time devoted to cervical ripening is not included when calculating the length of induction or diagnosing failed induction. So, we do not perform latent phase cesarean delivery (ie, failed induction) unless regular contractions and cervical change have failed to occur after 12-18 hours of oxytocin administration.
Practical Method for Applying Oral Misoprostol :
Take one tab misoprostol 200 mcg & dissolve it in a 200 ml water & give 25 ml to the patient every 3-4 hrs till favorable cervix for oxytocin.
– This technique for administration was offered as the prostaglandin is not equally distributed in the tablet. So, if you divided the tablet (200 mcg) into 4 hard parts, the total 200 mcg concentration may be in one single part. Thats why, its better to dissolve the tablet in water to be equally distributed in the solution then apply for the patient. Each 25 ml solution will contain 25 mcg PG E1.