Active phase labor arrest: revisiting the 2-hour minimum

Obstet Gynecol. 2001 Oct;98(4):550-4. doi: 10.1016/s0029-7844(01)01516-2.


Objective: To generate contemporary uterine activity and labor progress data for oxytocin-augmented labor, and assess whether 2 hours of active phase labor arrest with at least 200 Montevideo units justifies cesarean delivery.

Methods: Five hundred and one consecutive spontaneously laboring term women with abnormally progressive labor were managed by a standardized protocol: oxytocin and intrauterine pressure catheter with an intent to sustain at least 200 Montevideo units for 4 hours or more before cesarean for labor arrest. Uterine activity was measured, and maternal and neonatal outcomes were evaluated. With a sample of this size, the upper 95% confidence interval limit for an event with an observed rate of 1% is below 3%.

Results: During oxytocin augmentation, nulliparas who were delivered vaginally dilated at a median rate of 1.4 cm/hour versus 1.8 cm/hour for parous women. In both groups, the 5th percentile of cervical dilation rate was 0.5 cm/hour. Thirty-eight women experienced labor arrest for over 2 hours despite at least 200 sustained Montevideo units; 23 (61%) achieved a vaginal delivery. Rates of chorioamnionitis and endometritis for the 38 women were 26%. None of their infants sustained a serious complication, including brachial plexus injury, even though three of the 23 vaginal deliveries (13%) were complicated by shoulder dystocia.

Conclusion: These data demonstrate that oxytocin-augmented labor proceeds at substantially slower rates than spontaneous labor, and support our previous contention that the criteria of labor arrest for 2 hours, despite at least 200 sustained Montevideo units, are insufficiently rigorous for the performance of cesarean.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Cesarean Section / statistics & numerical data
  • Chorioamnionitis
  • Confidence Intervals
  • Endometritis
  • Female
  • Humans
  • Infant, Newborn
  • Labor Stage, First / drug effects*
  • Labor, Induced
  • Obstetric Labor Complications / drug therapy*
  • Oxytocin / pharmacology
  • Oxytocin / therapeutic use*
  • Parity
  • Pregnancy
  • Pregnancy Outcome
  • Prospective Studies
  • Time Factors
  • Uterine Contraction / drug effects
  • Uterine Monitoring


  • Oxytocin