Risk of cesarean section after induced versus spontaneous labor at term gestation

OBJECTIVE To investigate whether the cesarean section (CS) rate is increased in women whose labor was induced compared to those who had spontaneous labor at term pregnancy. METHODS A retrospective study was performed in women whose labor was either induced (induction group, n=497) or spontaneous (spontaneous group, n=878) at 37+0 to 41+6 weeks of gestation from January 2008 to June 2009. Maternal age, parity, body mass index (BMI), Bishop scores, gestational age, hypertension, diabetes, delivery mode, indications for CS, neonatal outcome were compared between the two groups. Multiple logistic regression analysis was used to examine the association between the CS rate and labor induction after adjusting for potential confounding variables. RESULTS CS (17.3% vs. 5.3%, P<0.001) and vacuum-assisted delivery (10.7% vs. 6.4%, P<0.001) rates were significantly higher in the induction group compared to the spontaneous group. The CS rate in the induction group was higher than the spontaneous group not only in nulliparous women (25.3% vs. 8.6%, P<0.001), but also in multiparous women (3.8% vs. 0.3%, P=0.002). However, after adjusting confounding factors, the higher CS rate was significantly associated with advanced maternal age, higher BMI, lower Bishop scores and nulliparity, with no demonstrable tie to labor induction. Neonatal outcome in the two groups were comparable. CONCLUSION Although CS rate was higher in women whose labor was induced than those who had spontaneous labor, this higher rate was associated with maternal age, BMI, Bishop scores and parity, but was not impacted by labor induction per se.