For a term (≥37 weeks) singleton pregnant woman with an intact cervix, cephalic presentation, no prior classical cesarean or uterine surgery, no placenta previa or vasa previa, no active bleeding, no severe fetal compromise, and no prostaglandin hypersensitivity, how should misoprostol be administered safely for induction in Canada?

Management of Misoprostol Induction in Canada

Recommended Dosing Protocol

For term singleton pregnancies with intact cervix and no contraindications, use 25 mcg misoprostol inserted into the posterior vaginal fornix every 3-6 hours, with a maximum of 4-5 doses over 24 hours. 1, 2

• The 25 mcg vaginal dose is the standard recommended by major obstetric societies due to optimal balance of efficacy and safety. 1
• Higher doses (50 mcg or more) are associated with increased uterine hyperstimulation and should be avoided. 1
• Each dose should be separated by at least 3-6 hours to allow assessment of uterine response. 1, 2
• Discontinue misoprostol once regular uterine contractions are established (typically 3 contractions per 10 minutes). 2, 3

Absolute Contraindications

Never use misoprostol in women with prior cesarean delivery or uterine surgery—this carries a 13% uterine rupture risk and is absolutely contraindicated. 4, 1

Additional absolute contraindications include:

• Classical cesarean scar or any full-thickness uterine incision 4
• Active cardiovascular disease (misoprostol causes hemodynamic instability) 4
• Placenta previa or vasa previa 4
• Advanced liver failure (misoprostol requires hepatic metabolism) 5
• Known prostaglandin hypersensitivity 1

Monitoring Requirements

Continuous electronic fetal monitoring and uterine activity monitoring are mandatory after each misoprostol dose for at least 3-4 hours. 1

• Monitor for uterine hyperstimulation (>5 contractions per 10 minutes or contractions lasting >2 minutes). 1
• Assess Bishop score before each subsequent dose—if cervix becomes favorable (Bishop ≥6), transition to oxytocin augmentation rather than additional misoprostol. 3
• Watch for signs of uterine rupture even in unscarred uteri, as rare cases have been reported. 1

Transition to Oxytocin

Once the cervix is favorable (Bishop score ≥6) or regular contractions are established, discontinue misoprostol and begin low-dose oxytocin if augmentation is needed. 2, 3

• Wait at least 4 hours after the last misoprostol dose before starting oxytocin to avoid hyperstimulation. 1
• Start oxytocin at 1-2 mU/min and increase by 1-2 mU/min every 40-60 minutes. 4
• Approximately 30-44% of patients will require oxytocin augmentation after misoprostol induction. 2, 3

Expected Outcomes

The mean induction-to-delivery interval with 25 mcg vaginal misoprostol is approximately 20-21 hours. 2

• 44% of patients deliver within 10 hours of induction. 3
• 65-70% achieve vaginal delivery. 3
• Cesarean section rate is approximately 25%, primarily for failed induction or fetal distress. 3
• Uterine hyperstimulation occurs in approximately 2-3% of cases with the 25 mcg dose. 2

Critical Safety Pitfalls to Avoid

Never combine misoprostol with other prostaglandins or use doses exceeding 25 mcg vaginally—this dramatically increases hyperstimulation risk. 1

• Do not use misoprostol for outpatient cervical ripening—all patients must be monitored in hospital. 1
• Do not administer additional doses if hyperstimulation occurs—the medication cannot be rapidly removed once absorbed. 6
• Do not use in women with suspected cephalopelvic disproportion, as this increases cesarean risk. 4
• Ensure adequate staffing for continuous monitoring, as misoprostol requires more intensive surveillance than mechanical methods. 1

Alternative for High-Risk Patients

For women with prior cesarean delivery or cardiac disease, use mechanical cervical ripening (Foley catheter) instead of misoprostol, as it carries zero uterine rupture risk. 5, 4

• Mechanical methods are equally effective for cervical ripening without the systemic effects of prostaglandins. 4
• This approach is strongly preferred when pharmacologic agents pose unacceptable risks. 5, 4