Early Induction Linked to Lower Odds of Cesarean Delivery

Diedtra Henderson

September 09, 2013

Elective induction of labor at 37 to 40 weeks of gestation was associated with significantly reduced risk for cesarean delivery but was not associated with increased odds of severe lacerations, neonatal intensive care unit admission, or perinatal death, according to a retrospective cohort study.

Blair G. Darney, PhD, MPH, from the Department of Medical Informatics and Clinical Epidemiology, Department of Obstetrics and Gynecology at Oregon Health and Science University in Portland, and colleagues report their findings in an article published online September 9 in Obstetrics & Gynecology.

Although the American College of Obstetricians and Gynecologists recommends against elective induction of labor at less than 39 weeks of gestation, little evidence exists about the health effects of such inductions, Dr. Darney and coauthors write.

The researchers analyzed 2006 California Department of Health Services data containing all deliveries for that calendar year, including deidentified birth and delivery records, maternal discharge data, and birth certificate data. The resulting sample of 362,154 women included those who delivered between 37 and 40 completed weeks of gestation. At each term week of gestation, the women who underwent elective induction were compared with women who had continued their pregnancy, delivering at a later gestational age.

"The odds of cesarean delivery were significantly lower among women in the induction without medical indication group at 37 completed weeks of gestation ([odds ratio (OR)] 0.44, 95% confidence interval [CI] 0.34–0.57), 38 weeks of gestation (OR 0.43, CI 0.38–0.50), 39 weeks of gestation (OR 0.46, CI 0.41–0.52), and 40 weeks of gestation (OR 0.57, CI 0.50–0.65). Although this relationship was especially strong among multiparous women, it held among nulliparous women at each week," Dr. Darney and colleagues write.

The authors found a higher incidence of hyperbilirubinemia at gestation weeks 37 and 38 in the induction group compared with the noninduction group. In addition, shoulder dystocia, brachial plexus, or clavicle injury were more common in the elective induction group at gestation week 39 compared with in the noninduction group.

In contrast, the researchers found no significant difference in risk for third- or fourth-degree lacerations, operative vaginal delivery, perinatal death, neonatal intensive care unit admission, respiratory distress, or macrosomia between the 2 groups at any gestation week studied.

The authors also note that at each term week of gestation, a greater proportion of women who were induced without medical indication were white, had private insurance, had completed high school, and had begun prenatal care in the first trimester compared with the expectant management group compared with those who were not induced.

"[W]e present evidence that induction without medical indication at term (37–40 weeks of gestation) is associated with reduced odds of cesarean delivery among both nulliparous and multiparous women with a previous vaginal delivery," Dr. Darney and colleagues conclude. "This holds for multiparous women at 38 and 39 completed weeks of gestation even when we vary assumptions about the timing of intrapartum indications."

Dr. Darney has disclosed receiving an Agency for Healthcare Research and Quality award. Another author disclosed receiving a National Institute on Aging grant. Two authors disclosed receiving a Health Resources and Services Administration/Maternal and Child Health grant. Another author disclosed support from the University of California, San Francisco; the National Institutes of Health; and the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The remaining authors have disclosed no relevant financial relationships.

Obstet Gynecol. Published online September 9, 2013.

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