What is Failed Induction of Labor
Failed induction of labor is defined as the inability to achieve the active phase of labor (≥4 cm dilation with ≥90% effacement, or ≥5 cm regardless of effacement) after at least 12–18 hours of oxytocin administration following membrane rupture, assuming maternal and fetal status remain reassuring. 1, 2
Diagnostic Criteria
The diagnosis of failed induction should not be made prematurely. The following timeline must be met before declaring an induction has failed:
- Minimum 12 hours of oxytocin administration after membrane rupture is required before considering cesarean delivery for "failed induction" during the latent phase 1, 3, 2
- Some evidence supports extending this to 12–18 hours of oxytocin after membrane rupture to maximize the chance of vaginal delivery 2, 4
- The cervix must have been adequately prepared: if the Bishop score was <5, at least 12 hours should be allowed after cervical ripening before starting this oxytocin timeline 1
Key Phases of Labor Context
Understanding failed induction requires distinguishing the latent from active phases:
- Latent phase: From onset of regular contractions until 6 cm cervical dilation 4
- Active phase: Begins at 6 cm dilation (or 4 cm with ≥90% effacement, or 5 cm regardless of effacement) 4, 5
- Failed induction specifically refers to failure to progress from latent to active phase despite adequate intervention 6, 5
Clinical Outcomes When Protocol Followed
When the 12-hour minimum oxytocin protocol is properly implemented, many women who appear to have "failed" at earlier timepoints ultimately achieve vaginal delivery:
- Among nulliparous women still in latent phase after 6 hours of oxytocin and ruptured membranes, 39% delivered vaginally when given adequate time 5
- After 9 hours, 28% of those remaining in latent phase still delivered vaginally 5
- Even after 12 hours in latent phase, 13% of nulliparas achieved vaginal delivery 5
- In parous women, failed induction was essentially eliminated as a cesarean indication when the 12-hour protocol was followed 5
Primary Predictive Factor
Cervical status at the time of induction is the most important predictor of induction outcome:
- Women with an unfavorable cervix (Bishop score ≤3) have a 65.4% cesarean rate, with more than two-thirds due to failed induction 7
- The Bishop score evaluates cervical dilation, effacement, consistency, position, and fetal station 8
- A Bishop score <5 indicates an unfavorable cervix requiring cervical ripening agents before oxytocin 1, 8
Common Pitfall to Avoid
The most critical error is diagnosing failed induction too early—particularly before 12 hours of oxytocin after membrane rupture. This leads to unnecessary cesarean deliveries in women who would have achieved vaginal delivery with more time. 1, 2, 4 The mean cervical dilation at cesarean for "failed induction" in one study was only 3.5 cm, suggesting many of these diagnoses were premature. 7
Distinction from Other Labor Complications
Failed induction must be differentiated from:
- Arrested active phase: No cervical change for >4 hours with adequate contractions and ruptured membranes, or >6 hours without adequate contractions, occurring after reaching active phase 4
- Cephalopelvic disproportion: Typically diagnosed at more advanced cervical dilation (mean 5.7 cm) 7
- Fetal distress: A separate indication for cesarean unrelated to labor progress 7