Failed Prostaglandin Induction

Failed prostaglandin induction is failure of the cervix to ripen, or labour to start, after a full course of misoprostol or dinoprostone. It results from a poorly responsive cervix, wrong dates, scarring, malposition or an unnecessary induction. It matters because induction should not be repeated blindly, and the choice between rest, another method and caesarean section depends on the indication and condition of mother and baby.

• Misoprostol course: 25 micrograms vaginal 6-hourly for up to 4 doses. Dinoprostone: 10 mg vaginal insert for up to 24 hours.
• Risk factors: first pregnancy, body mass index above 30 kg/m2, Bishop score below 4, post term pregnancy, previous cervical surgery.
• Prostaglandins cannot be used in a scarred uterus.

Women have taken the full prostaglandin course with little cervical change and few or irregular contractions. Some have long painful contractions without effacement.

• Cervix long, firm and closed or 1 to 2 cm dilated.
• Fetal heart rate usually normal.
• Differential diagnosis: wrong gestation, prolonged latent phase, hyperstimulation with exhaustion, cervical scarring, drug expelled, inappropriate indication.
• Complications: prolonged induction, exhaustion, infection if membranes are ruptured, tachysystole, fetal distress, caesarean section, neonatal admission.

The diagnosis is made by repeating the Bishop score after the final dose.

• Bishop score: dilatation 0 to 3, effacement 0 to 3, station 0 to 3, consistency 0 to 2, position 0 to 2; 6 or more is favourable.
• Check that all doses were given, the interval used, and that no insert was expelled.
• Cardiotocography; ultrasound for gestation, fetal weight and presentation.
• Review of the indication and urgency of birth.

The principle is to review the indication, wait or repeat ripening when safe, and deliver by caesarean section when birth is urgent.

• Supportive: rest and feeding for 12 to 24 hours if mother and baby are well; membrane sweeping at examination; outpatient waiting when the indication allows; continuous cardiotocography in high risk women; explain the options.
• Pharmacological: repeat misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or oral 25 micrograms 2-hourly for up to 6 doses after the rest period; Foley catheter 30 mL balloon alone or with oxytocin 10 IU in 1 litre Ringer's lactate (10 mU/mL) started at 12 mL per hour (2 mU/minute) and doubled every 30 minutes to a maximum of 192 mL per hour (32 mU/minute), starting oxytocin 6 hours after the last misoprostol dose or 30 minutes after removing the dinoprostone insert; mifepristone 200 mg oral once followed 24 hours later by misoprostol 25 micrograms vaginal 6-hourly where available; cefazolin 2 g IV before caesarean section; oxytocin 10 IU IM after birth, then 20 IU in 1 litre at 125 mL per hour for 4 hours.
• Procedures: Foley catheter ripening for 12 to 24 hours; amniotomy when the cervix is 2 to 3 cm dilated and the head is engaged; caesarean section for fetal compromise, chorioamnionitis, a strong indication to deliver, or failure after two courses.
• Special groups: a uterine scar avoids all prostaglandins and uses a Foley catheter alone or caesarean section; women with growth restriction or hypertension have shorter waits.
• Red flags: tachysystole, abnormal fetal heart rate, bleeding, scar pain, fever above 38 degrees Celsius.
• Follow-up: repeat the Bishop score after each course; maternal temperature 4-hourly if membranes are ruptured; review at 6 weeks; counselling on the next induction.