Elective Induction of Labor at 41 Weeks or Longer May Reduce Risk for Cesarean Delivery

From Medscape Medical News
Laurie Barclay, MD

August 17, 2009 — Elective induction of labor at 41 weeks of gestation or later is associated with a decreased risk for cesarean delivery and meconium-stained amniotic fluid, according to the results of a systematic review reported in the August 18 issue of the Annals of Internal Medicine. However, the reviewers warn against translating these findings to actual practice.

"The rates of induction of labor and elective induction of labor are increasing," write Aaron B. Caughey, MD, MPP, MPH, PhD, from Stanford University in California, and colleagues. "Whether elective induction of labor improves outcomes or simply leads to greater complications and health care costs is commonly debated in the literature."

The goal of this review was to compare the benefits and harms of elective induction of labor with those of expectant management of pregnancy. The reviewers searched Medline through February 2009; Web of Science, CINAHL, and the Cochrane Central Register of Controlled Trials through March 2009; reference lists of retrieved studies; and previously published systematic reviews for English-language articles describing experimental and observational studies of elective induction of labor.

Two of the reviewers abstracted information regarding study design, patient characteristics, methodologic quality, and outcomes including cesarean delivery and maternal and neonatal morbidity. Of 6117 articles identified, 36 met inclusion criteria, of which 11 were randomized controlled trials (RCTs) and 25 were observational studies.

Compared with elective induction of labor, expectant management of pregnancy was associated in 9 RCTs with a higher odds ratio (OR) of cesarean delivery (OR, 1.22; 95% confidence interval [CI], 1.07 – 1.39; absolute risk difference, 1.9 percentage points; 95% CI, 0.2 – 3.7 percentage points). Risk for cesarean delivery was higher in women at or beyond 41 completed weeks of gestation who were managed expectantly (OR, 1.21; 95% CI, 1.01 – 1.46). However, this difference was not statistically significant in women at less than 41 completed weeks of gestation (OR, 1.73; 95% CI, 0.67 – 4.5).

Compared with women who had elective induction of labor, those who were managed expectantly were more likely to have meconium-stained amniotic fluid (OR, 2.04; 95% CI, 1.34 – 3.09).

"RCTs suggest that elective induction of labor at 41 weeks of gestation and beyond is associated with a decreased risk for cesarean delivery and meconium-stained amniotic fluid," the review authors write. "There are concerns about the translation of these findings into actual practice; thus, future studies should examine elective induction of labor in settings where most obstetric care is provided."

Limitations of this review include that there were no recent RCTs of elective induction of labor at less than 41 weeks of gestation. The 2 studies conducted at less than 41 weeks of gestation were of poor quality, and the findings could not be generalized to current practice.

In an accompanying editorial, George A. Macones, MD, MSCE, from Washington University in St. Louis School of Medicine in Missouri, notes the need for well-designed RCTs of induction vs expectant management at 39 to 41 weeks that are sufficiently powered to evaluate critical subgroups, such as parity and cervical examination at randomization. In addition to studying rates of cesarean delivery, he also recommends studying the effect of new strategies on healthcare utilization and costs.

"Elective inductions are on the rise," Dr. Macones writes. "This development may not be as bad as obstetricians have traditionally believed. I hope that Caughey and colleagues' excellent systematic review will spur obstetricians to rethink and, more important, to more carefully research the role of elective induction of labor at and beyond 39 weeks."

Ann Intern Med. 2009;151:252–263, 281–282.