Is there an increased risk of cesarean section in obese women after induction of labor? A retrospective cohort study

BACKGROUND: Obesity is increasing in Sweden and is also of huge global concern. Obesity increases the risk of complications during pregnancy and the need for the induction of labor. Induction of labor increases the number of complications during delivery, leading to women with more negative birth experience. This study investigated how maternal body mass index (BMI) during antenatal care enrollment affects labor outcomes (proportion of cesarean section at induction of labor). METHOD: This was a retrospective cohort study of 3772 women with mixed parity and induction of labor at Soderhospital, Stockholm, in 2009–2010 and 2012–2013. The inclusion criteria were simplex, ≥34 gestational weeks, cephalic presentation and no previous cesarean section. The women were grouped according to BMI, and statistical analyzes were performed to compare the proportion of cesarean sections after induction of labor. The primary outcome was the proportion of cesarean section after induction of labor divided by group of maternal BMI. The secondary outcomes were postpartum hemorrhage >1000 ml, time of labor, fetal outcome data, and indication for emergency cesarean section. RESULT: The induction of labor in women with a high BMI resulted in a significantly increased risk of cesarean section, with 18.4–24.1% of deliveries, depending on the BMI group. This outcome persisted after adjustment in women with BMI 25–29.9 (aOR 1.4; 95% CI; 1.1–1.7) and BMI 30–34.9 (aOR 1.5; 95% CI; 1.1–2.1). There was also a significantly higher risk for CS among primiparous women (aOR 3.6; 95% CI; 2.9–45) and if the newborn weighted ≥ four kilos (aOR 1.6; 95% CI; 1.3–2.0). CONCLUSION: Our findings show that a higher BMI increased the risk of cesarean section after induction of labor in the groups with BMI 25–34.9. Parity seems to be the strongest risk factor for CS regardless other variables.