BACKGROUND AND PURPOSE:

• Tita et al. (Obstetrics & Gynecology, 2021) compared risks of maternal and perinatal outcomes by completed week of gestation from 39 weeks in low-risk nulliparous patients undergoing expectant management

METHODS:

• Secondary analysis of the ARRIVE trial
  • Multicenter RCT
• Participants
  • Low risk nulliparous pregnant women
  • Non-anomalous neonates
  • Women who were randomized to the expectant management group and attained 39w0d weeks of gestation in the original ARRIVE trial
• Exposures
  • 39 weeks gestation (39w0d to 39w6d)  
  • 40 weeks gestation (40w0d to 40w6d)
  • 41 to 42 weeks gestation (41w0d to 42w2d)  
• Data analysis
  • For multivariable analysis, P<.0125 was used to indicate statistical significance for coprimary outcomes
• Primary outcomes
  • Cesarean delivery
  • Perinatal composite: Death | Respiratory support | 5-minute Apgar ≤3 | HIE | Seizure | Sepsis | Meconium aspiration syndrome | Birth trauma | Intracranial or subgleal hemorrhage | Hypotension requiring vasopressor support
• Secondary outcomes
  • Maternal composite: Transfusion | Surgical intervention for PPH | ICU admission
  • Hypertensive disorders of pregnancy
  • Peripartum infection
  • Neonatal intermediate or intensive care unit admission

RESULTS:

• 2502 participants underwent expectant management with delivery at the following weeks gestation
  • 39 weeks: 38.5%
  • 40 weeks: 44.4%
  • 41 to 42 weeks: 17.1%
• Prevalence of medically indicated delivery
  • Overall: 37.9%
  • 39 weeks: 23.8%
  • 41 to 42 weeks: 80.3%
  • Reasons for delivery at 39 or 40 completed weeks
    • Postterm induction (at 40 completed weeks) | Hypertensive disorders of pregnancy | PROM
• The frequency of both cesarean and the perinatal composite increased with increased gestational age at delivery
  • Cesarean (P < 0.001)
    • 39 weeks: 17.3%
    • 40 weeks: 22.0%
    • 41 to 42 weeks: 37.5%
  • Perinatal composite (P = 0.03)
    • 39 weeks: 5.1%
    • 40 weeks: 5.9%
    • 41 to 42 weeks: 8.2%
    • After adjustment, perinatal composite still remained 56% higher in the 41 to 42 group, but was not statistically significant
• The frequency of hypertensive disorders of pregnancy decreased with increasing gestation time (P = 0.001)
  • 39 weeks: 16.4%
  • 40 weeks: 12.1%
  • 41 to 42 weeks: 10.8%
• There was an increased risk of cesarean at 41 to 42 weeks vs 39 weeks
  • Adjusted relative risk (RR) 1.93 (95% CI, 1.61 to 2.32)
• There was a decreased risk of hypertensive disorders of pregnancy with greater gestational age vs 39 weeks
  • 40 week: aRR 0.71 (95% CI, 0.58 to 0.88)
  • 41 to 42 weeks: aRR 0.61 (95% CI, 0.45 to 0.82)
• None of the other outcomes were found to be significant

CONCLUSION:

• For nulliparous women with low-risk pregnancies, expectant management after 39w0d increased the risk for cesarean and medically indicated delivery
  • There was no change in perinatal composite outcome after adjustments
• Risks associated with stillbirth and neonatal death could not be assessed due to sample size
• The authors conclude

Overall, these data provide important insights into the anticipated course of expectant management of low-risk nulliparous patients who would typically be candidates for elective induction of labor

The information will be useful for counseling patients regarding ongoing risks of expectant management, and optimizing shared decision making

Learn More – Primary Sources:

Maternal and Perinatal Outcomes of Expectant Management of Full-Term, Low-Risk, Nulliparous Patients

Related ObG Topics:

The ARRIVE Trial and Professional Guidance: Elective 39 Week Induction to Reduce the Risk of Cesarean Section

Induction at 41 Weeks vs Expectant Management: Results from the INDEX Trial

Low-Risk Multiparous Women: Induction of Labor at 39 Weeks or Expectant Management?

Secondary Analysis of ARRIVE RCT: The Association Between Amniotomy During Induction and Cesarean Delivery