Induction of labor is a major component of practice. Just under a third of multiparous women undergo induction, but 43 percent of nulliparous women have induced labor.
“Induction of labor is likely to become more common with increasing maternal age, obesity, hypertensive disorders and obesity,” said Mary Catherine Tolcher, MD, MS, assistant professor of obstetrics, Mayo Clinic Rochester. “And there can be good reasons for it.”
The leading medical indications for induction at Mayo include late-term pregnancy, fetal indications, PROM, gestational hypertension and diabetes, said Dr. Tolcher, who spoke at a Saturday afternoon Clinical Seminar.
The benefits of induced labor are clear, she said. Induced labor avoids maternal and fetal risks of continuing pregnancy, avoids risks of late-term pregnancy, allows the timing of labor to be controlled in cases where delivery in a particular facility is appropriate and may be an alternative to cesarean delivery.
The risks are equally clear. Induction can mean prolonged hospitalization before delivery, increased likelihood of more intrusive interventions, increased risk of postpartum hemorrhage and increased likelihood of cesarean delivery.
“Whether induction of labor increases the risk of cesarean delivery is like a lot of things in medicine,” Dr. Tolcher said. “It depends on your comparison group.”
Compared to spontaneous labor, induction does increase the likelihood of cesarean delivery. Depending on the study, the odds ratio for cesarean delivery following induction of labor is somewhere between 1.9 and 3.5.
But compared to expectant management, induction is probably not associated with an increased risk of cesarean delivery.
Both conclusions are based on retrospective cohort data. The first randomized control trial of induction vs. expectant management, the ARRIVE trial, is expected to complete data collection later this year, she said.
Several methods have been developed to induce labor, including pharmacologic cervical ripening using prostaglandins and mechanical ripening using a Foley catheter. Other techniques include oxytocin, oxytocin plus cervical ripening and amniotomy.
All have been shown to be effective in clinical trials, Dr. Tolcher said. Cervical ripening appears to be more effective than oxytocin alone, while there appears to be little difference in outcomes between prostaglandins and Foley. The most recent data, reported at the Society for Maternal-Fetal Medicine in 2016, found shorter time to delivery with combination methods with no difference in cesarean delivery rates.
Amniotomy is also effective, but comparisons of early amniotomy, less than five cm, with late amniotomy, five cm or larger, suggested the latter may be more appropriate. Early amniotomy results in shorter labor but higher rates of chorioamnionitis and significant fetal umbilical cord compression.
Mayo has its own protocol for induction, Dr. Tolcher reported. Cases for the following week are reviewed during regular staff meetings on Fridays and the L&D charge nurse has the authority to issue a hard stop for non-indicated cases.
Current indications include advanced maternal age, cholestasis, diabetes, fetal issues, hypertensive disorders, obesity, preterm premature rupture of membranes, prolonged pregnancy, prior stillbirth and unstable presentation. Depending on the indication, the pregnancy must be in week 37 and later.
Cervical ripening is the initial procedure, followed by oxytocin as needed and amniotomy at the provider’s discretion. A failed induction is 24 hours of oxytocin or 18 hours of oxytocin plus rupture of membranes.
“You need a good discussion of induction with the mom before any decisions are made,” Dr. Tolcher said. “It is easy to assume that if labor is induced, it will happen quickly. This can be a long, drawn out procedure.”