By John C. Hobbins, MD

Professor, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora

Dr. Hobbins reports no financial relationships relevant to this field of study.

Synopsis: A recent study in patients having non-medically indicated inductions of labor has shown that this option is associated with higher cesarean section rate at 38 and 40 weeks, but not, interestingly, at 39 weeks, at which time there was a lower rate of peripartum infections, fewer newborn special care unit admissions, but longer labors. However, these data do not speak for empiric induction of labor at 39 weeks without medical indication.

Source: Bailit JL, et al. Nonmedically indicated induction vs expectant management in term nulliparous women. Am J Obstet Gynecol 2015;212:103.e1-7.

Inductions of labor (IOL) alarmingly increased from 2% in 1991 to 8% 2006.1 Then, in another upward swing, a 2009 ACOG Practice Bulletin stated that 22% of all deliveries in the United States were linked with IOL.2 During that same time frame, there had been a concomitant rise in the cesarean section rate (CSR) with, at last count, a rate of 32.8%.3 One would expect a direct relationship between the two trends in medically indicated IOLs since the reason alone for the inductions would predispose those patients to a higher CSR, but it is unclear how much non-medically indicated IOLs effect the CSR.

For good reason, there has been a move on the part of official medical bodies and many individual hospitals to discourage elective cesarean section in early-term patients (at < 39 weeks), since studies have shown a higher rate of neonatal morbidity at this time compared with 39 weeks.4 In an attempt to see if this trend is the same for elective inductions, authors from the Maternal-Fetal Medicine Units (MFMU) network evaluated, by secondary analysis, 31,169 patients in 25 centers over a 3-year period (2008-2011).5 They compared neonatal outcomes of those babies delivered between 38 and 41 weeks by non-medical IOL and those in whom no intervention was attempted (“expectant management”).

At 39 weeks they found no difference in composite neonatal adverse outcomes, but there was a lower rate of admissions to the NICU (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.47-0.93) and maternal peripartum infection (OR, 0.66; 95% CI, 0.49-0.86) with non-medically indicated IOL vs expectant management. At 39 weeks there was no statistically significant difference in CSR (25.8% vs 23.8% with an OR of 1.13; 95% CI, 0.94-1.36). However, those patients with non-medically indicated IOL spent 3 hours longer in the hospital between admission and delivery. If inductions were attempted at 38 weeks or 40 weeks, the CSR was significantly higher with an OR of 1.50 (95% CI, 1.08-2.08) and OR of 1.3 (95% CI, 1.15-1.46), respectively.

COMMENTARY

The results show that inductions for non-medical reasons between 39 and 41 weeks resulted in modest or no neonatal benefit, a lower rate of peripartum infection, but an increase in CSR at 38 and 40 weeks.

It is important to emphasize that the data in the MFMU study again endorse the admonition to hold off delivering early-term babies electively without an indication in view of the 50% increase in the CSR without neonatal benefit at 38 weeks. Although suggesting a possible maternal benefit to IOL at 39 weeks, the results in no way represent a “license to induce” all patients at this time. Why?

  1. As pointed out in the companion editorial by Caughey,6 expectant management includes patients who can develop problems later in pregnancy, such as preeclampsia, intrauterine growth restriction, glucose intolerance, and even later, post-term pregnancy. The analysis did not compare non-medically indicated IOL with spontaneous labor at the same gestational age. In effect, the benefit of a pre-emptive (and non-physiologic) strike at 39 weeks in uncomplicated patients might only be to protect normal fetuses from completely unexpected events to come.
  2. This was a retrospective analysis and not a randomized clinical trial, which would better test the hypothesis.
  3. Since cost containment is a factor in today’s delivery of care, another study did not find IOL at 39 weeks to be cost-effective,7 and this did not include the extra 3 hours in the hospital noted in the MFMU study.

At 41 weeks, studies have found IOL to be efficacious and cost-effective.8 However, induction decisions (without medical indication) in the window between 39 and 41 weeks should await further study.

References

  1. Murthy K, et al, Trends in induction of labor at early-term gestation. Am J Obstet Gynecol 2011;204:435.e1-6.
  2. American College of Obstetrics and Gynecology Practice Bulletin No. 107: Induction of labor; 2009.
  3. US Center of Health Statistics, 2011.
  4. Cheng YW, et al. Perinatal outcomes in low-risk term pregnancies: Do they differ by week of gestation? Am J Obstet Gynecol 2008;199:370.e1-7.
  5. Bailit JL, et al. Nonmedically indicated induction vs expectant management in term nulliparous women. Am J Obstet Gynecol 2015;212:103.
  6. Caughey AB. Non-medically indicated induction of labor: Are the benefits worth the cost? Am J Obstet Gynecol 2015;212:7-8.
  7. Caughey AB, et al. Maternal and neonatal outcomes of elective induction of labor. Evid Rep Technol Assess 2009;176:1-257.
  8. Kaimal AJ, et al. Induction of labor at 41 weeks. Is it cost effective? Am J Obstet Gynecol 2011;204.e1-9.