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Intrapartum cesarean delivery in nulliparas: risk factors compared by two analytical approaches



To determine risk factors for cesarean delivery in nulliparas at labor admission.

Study Design:

Nulliparas with live-born, singleton gestations 37 weeks in spontaneous or induced labor were analyzed from the Consortium on Safe Labor database in a retrospective observational study. Classification and regression tree (CART) and multivariate logistic regression analysis determined risk factors for cesarean delivery.


Of the 66 539 nulliparas, 22% had a cesarean delivery. In the CART analysis, the first cervical dilation exam was the first branch followed by body mass index (BMI). Cesarean deliveries occurred in 45%, 25%, 14% and 10% of deliveries at <1 , 1 to 3, 4 and 5 cm dilated, respectively. The BMI influence was most evident in the <1 cm dilation category with 26% of BMI <25 kg m−2 and 66% of BMI 40 kg m−2 having a cesarean delivery. The fewest cesarean deliveries (5%) occurred in those 5 cm and BMI <25 kg m−2. In the multivariate regression analysis, first cervical dilation exam <1 cm (odds ratio (OR) 5.1, 95% confidence interval (CI): 4.5 to 5.7; reference 5 cm) and BMI 40 kg m−2 (OR 5.1, 95% CI: 4.6 to 5.7; reference BMI <25.0 kg m−2) had the highest odds for cesarean delivery.


Cervical dilation on admission followed by BMI were the two most important risk factors for cesarean delivery identified in both CART and multivariate regression analysis.

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The data included in this paper were obtained from the Consortium on Safe Labor, which was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, through Contract No. HHSN267200603425C. Institutions involved in the Consortium include, in alphabetical order: Baystate Medical Center, Springfield, MA; Cedars-Sinai Medical Center Burnes Allen Research Center, Los Angeles, CA; Christiana Care Health System, Newark, DE; Georgetown University Hospital, MedStar Health, Washington, DC; Indiana University Clarian Health, Indianapolis, IN; Intermountain Healthcare and the University of Utah, Salt Lake City, UT; Maimonides Medical Center, Brooklyn, NY; MetroHealth Medical Center, Cleveland, OH; Summa Health System, Akron City Hospital, Akron, OH; The EMMES Corporation, Rockville MD (Data Coordinating Center); University of Illinois at Chicago, Chicago, IL; University of Miami, Miami, FL; and University of Texas Health Science Center at Houston, Houston, TX, USA. The named authors alone are responsible for the views expressed in this manuscript, which does not necessarily represent the decisions or the stated policy of the NICHD.

This study was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, through a contract (Contract No. HHSN267200603425C) for the original Consortium on Safe Labor study; Grant No. K23 HD076010 from the NICHD and NIH (to MK); and University of Illinois at Chicago (UIC) Center for Clinical and Translational Science (CCTS), Award No. UL1RR029879 from the National Center for Research Resources.

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Correspondence to M A Kominiarek.

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This study was presented in part as a poster at the Annual Meeting for the Society of Maternal Fetal Medicine in San Francisco, California on 11 February 2011. Drs Kominiarek, VanVeldhuisen, Gregory and Hibbard all received funding from the NIH/NICHD for the original Consortium on Safe Labor project. Ms Kim and Dr Fridman declare no potential conflict of interest. Dr Kominiarek currently has a K23 Mentored Career Development Award from the NIH/NICHD.

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Kominiarek, M., VanVeldhuisen, P., Gregory, K. et al. Intrapartum cesarean delivery in nulliparas: risk factors compared by two analytical approaches. J Perinatol 35, 167–172 (2015).

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