Cesarean section after induction of labor compared with expectant management: no added risk from gestational week 39

Objective. To compare induction of labor and expectant management by gestational week with regard to the need for cesarean section (CS) in labor. Design. Cohort study. Setting. National study based on the Danish Birth Registry. Population. Aggregated data from 230 528 deliveries from 2004 until mid-year 2009. Women with cesarean section before labor, previous cesarean, preterm birth, breech presentation, multiple pregnancy and specified medical illnesses in pregnancy were excluded. Methods. We compared by gestational week nulliparous and parous women who were either induced or had expectant management until later spontaneous or induced labor. For each of five comparisons, we conducted multivariable logistic regression analysis, controlling for body mass index, age, smoking in pregnancy and use of epidural analgesia during labor. Main Outcome Measure. Rate of CS in labor. Results. From gestational week 39 and thereafter, there was no difference with regard to CS rates in labor among nulliparous and parous women when comparing women with induced labor and those women who waited for a later labor, either induced or spontaneous. The odds ratios (with confidence intervals) for CS in labor in nulliparous women were 0.99 (0.84-1.17), 1.16 (1.04-1.30), 1.04 (0.94-1.15), 1.00 (0.92-1.10) and 0.97 (0.88-1.07) for weeks 37-41, respectively. For parous women the corresponding figures were 1.72 (1.35-2.20), 1.27 (1.04-1.55), 1.15 (0.95-1.39), 1.18 (0.99-1.40) and 1.07 (0.87-1.32), respectively. Conclusions. Induction of labor provides a sound tool when counseling a woman either going past term or presenting with a problem, even if it is not a severe medical illness.