BACKGROUND AND PURPOSE:

•  Son et al. (Obstetrics & Gynecology, 2021) compared high-dose to standard dosing for labor augmentation

METHODS:

• Double-blind randomized clinical trial
• Participants
  • Nulliparous, admitted with spontaneous onset of labor
  • ≥36 weeks
  • Undergoing augmentation of labor
• Interventions
  • High-dose oxytocin regime
    • Initial and incremental rates of 6 milliunits/min
  • Standard-dose regime
    • Initial and incremental rates of 2 milliunits/min
• Protocol
  • No maximum rate limit due to lack of evidence for specific safety threshold
  • Infusion was titrated based on frequency of contractions and avoidance of abnormal fetal heart rate patterns
• Sample size
  • Target difference: 6.6% absolute reduction in rate of the primary outcome
  • 80% power | Two-sided type I error rate of 5%
  • Sample size: 501 per group
• Primary outcome
  • Cesarean birth
• Secondary outcomes
  • Labor duration | Clinical chorioamnionitis | Endometritis | PPH | 5 min Apgar ≤3 | Umbilical artery acidemia | NICU admission | Perinatal death | Severe perinatal morbidity composite

RESULTS:

• High dose: 502 women | standard dose: 501 women
  • Population: Majority were white, married or living as married, and had commercial insurance
  • Baseline characteristics between groups were similar
• No difference in incidence of cesarean birth between the two groups
  • High dose: 14.5%
  • Standard dose: 14.4%
  • Relative risk (RR) 1.01 (95% CI, 0.75 to 1.37)
• The high-dose group had a significantly
  • Shorter mean labor duration (P < 0.001)
    • High dose: 9.1 hours
    • Standard dose: 10.5 hours
  • Lower chorioamnionitis incidence
    • High dose: 10.4%
    • Standard dose: 15.6%
    • RR 0.67 (95% CI, 0.48 to 0.92)
• Umbilical artery acidemia was significantly less frequent in the high-dose group in complete case analysis, but when missing data was accounted for (through multiple imputation) there was no significant difference
  • RR 0.55 (95% CI, 0.29 to 1.04)
• No significant differences were identified for other secondary outcomes

CONCLUSION:

• Augmenting labor with high-dose vs standard-dose oxytocin in nulliparous women did not reduce cesarean rates, but did lead to shorter duration of labor and a lower incidence of chorioamnionitis
• The authors state

Shorter time to delivery and the evidence suggesting decreased maternal and perinatal complications in the high-dose group, support the view that a high-dose regimen may be preferred in this population

Learn More – Primary Sources:

High-Dose Compared With Standard-Dose Oxytocin Regimens to Augment Labor in Nulliparous Women

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