Labor induction and cesarean delivery: A prospective cohort study of first births in Pennsylvania, USA.
Mode of delivery at first childbirth largely determines mode of delivery at subsequent births, so it is particularly important to understand risk factors for cesarean delivery at first childbirth. In this study, we investigated risk factors for cesarean delivery among nulliparous women, with focus on the association between labor induction and cesarean delivery.



A prospective cohort study of 2851 nulliparous women with singleton pregnancies who attempted vaginal delivery at hospitals in Pennsylvania, 2009-2011, was conducted. We used nested logistic regression models and multiple mediational analyses to investigate the role of three groups of variables in explaining the association between labor induction and unplanned cesarean delivery-the confounders of maternal characteristics and indications for induction, and the mediating (intrapartum) factors-including cervical dilatation, labor augmentation, epidural analgesia, dysfunctional labor, dystocia, fetal intolerance of labor, and maternal request of cesarean during labor.



More than a third of the women were induced (34.3%) and 24.8% underwent cesarean delivery. Induced women were more likely to deliver by cesarean (35.9%) than women in spontaneous labor (18.9%), unadjusted OR 2.35 (95% CI 1.97-2.79). The intrapartum factors significantly mediated the association between labor induction and cesarean delivery (explaining 76.7% of this association), particularly cervical dilatation <3 cm at hospital admission, fetal intolerance of labor, and dystocia. The indications for labor induction only explained 6.2%.



Increased risk of cesarean delivery after labor induction among nulliparous women is attributable mainly to lower cervical dilatation at hospital admission and higher rates of labor complications.
Departments of Public Health Sciences and Obstetrics and Gynecology, Penn State University College of Medicine, Hershey, PA, USA.
Kristen H
0000-0002-5376-2581
KH
Kjerulff
Sewanee: The University of the South, Sewanee, TN, USA.
Laura B
LB
Attanasio
Connell School of Nursing, Boston College, Boston, MA, USA.
Joyce K
0000-0002-0465-9043
JK
Edmonds
Division of Health Policy and Management, University of Minnesota, School of Public Health, Minneapolis, MN, USA.
Katy B
KB
Kozhimannil
Department of Obstetrics and Gynecology, Penn State University College of Medicine, Hershey, PA, USA.
John T
JT
Repke
D000293:Adolescent; D000328:Adult; D015360:Analgesia, Epidural / Q000706:statistics & numerical data; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D036861:Delivery, Obstetric; D004420:Dystocia / Q000453:epidemiology; D005260:Female; D006801:Humans; D007747:Labor Stage, First; D007751:Labor, Induced; D016015:Logistic Models; D010120:Oxytocics / Q000627:therapeutic use; D010298:Parity; D010414:Pennsylvania; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D055815:Young Adult
D010120:Oxytocics
cervical dilatation; cesarean delivery; labor induction; nulliparous