Of the 1.5 million nulliparous women who deliver annually in the United States, more than 50% are low-risk pregnancies. Among clinicians, there is a hesitancy to offer elective induction of labor to low-risk nulliparous women, mainly due to early observational studies that noted an association between elective induction of labor and higher rates of cesarean delivery (CD) and other adverse maternal and perinatal outcomes. 1-3 This reluctance over time has permeated throughout the ObGyn specialty and is culturally embedded in contemporary practice. The early observational studies lacked proper comparison groups because outcomes of women undergoing induction (elective and medically indicated) were compared to those in spontaneous labor. Since women who are being induced do not have the option to be in spontaneous labor, the appropriate comparator group for women undergoing elective induction is women who are being managed expectantly.
ARRIVE addresses appropriate comparator groups
Challenging this pervaded practice, in August 2018, Grobman and colleagues published the findings of the ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management).4 This trial, conducted by Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network, recruited participants from 41 geographically dispersed centers in the United States. Nulliparous women with low-risk pregnancies between 34 0/7 and 38 6/7 weeks were randomly assigned to either induction of labor at 39 0/7 to 39 4/7 weeks or to expectant management, which was defined as delaying induction until 40 5/7 to 42 2/7 weeks. The objective of the ARRIVE trial was to determine if, among low-risk nulliparous women, elective induction of labor at 39 weeks, compared with expectant management, would reduce the rate of adverse outcomes.
The primary outcome was a composite: perinatal death or severe neonatal complications (need for respiratory support within 72 hours of birth, Apgar score of ≤ 3 at 5 minutes, hypoxic-ischemic encephalopathy, seizures, infection [confirmed sepsis or pneumonia], meconium aspiration syndrome, birth trauma [bone fracture, neurologic injury, or retinal damage], intracranial or subgaleal hemorrhage, or hypotension requiring vasopressor support). The secondary outcomes included CD, hypertensive disorders of pregnancy, number of hours in the labor and delivery (L&D) unit, length of postpartum hospital stay, and assessment of satisfaction with labor process.
Mothers induced at 39 weeks fared better, while neonatal outcomes were similar. Of 22,533 eligible women, 6,106 (27%) were randomized: 3,062 were assigned to the induction group, and, 3,044 to the expectant management group. The primary composite outcome—perinatal death or severe neonatal complications—was similar in both groups (4.3% in the induction group vs 5.4% in the expectant management group).
However, women who were induced had significantly lower rates of:
- CD (18.6% with induction vs 22.2% for expectant management; relative risk [RR], 0.84; 95% confidence interval [CI], 0.76–0.93)
- hypertensive disorders of pregnancy (9.1% vs 14.1%; RR, 0.64; 95% CI, 0.56–0.74)
- neonatal respiratory support (3.0% vs. 4.2%; RR, 0.71; 95% CI, 0.55–0.93).
In addition, although women in the induction group had a longer stay in the L&D unit (an expected outcome), the overall postpartum length of stay was shorter. Finally, women in the induction group had higher patient satisfaction scores, with less pain and more control reported during labor.
Continue to: What about uncommon adverse outcomes compared at 39 vs 41 weeks?