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Systems Factors in Obstetric Care: The Role of Daily Obstetric Volume

Snowden, Jonathan M. PhD; Darney, Blair G. PhD, MPH; Cheng, Yvonne W. MD, PhD; McConnell, K. John PhD; Caughey, Aaron B. MD, PhD

doi: 10.1097/AOG.0b013e3182a2dd93
Original Research

OBJECTIVE: To evaluate whether relatively high-volume days are associated with measures of obstetric care in California hospitals.

METHODS: This is a population-based retrospective cohort study of linked data from birth certificates and antepartum and postpartum hospital discharge records for California births in 2006. Birth asphyxia and nulliparous, term, singleton, vertex cesarean delivery rates were analyzed as markers of quality of obstetric care. Rates were compared between hospital-specific relatively high-volume days (days when the number of births exceeded the 75th percentile of daily volume for that hospital) and low-volume or average-volume days. Analyses were stratified by weekend and weekday and overall hospital obstetric volume. Multivariable logistic regression was used to control for confounders.

RESULTS: On weekends, relatively high-volume days were significantly associated with an elevated risk of asphyxia (27 out of 10,000 compared with 17 out of 10,000; P=.013), whereas no association was present on weekdays (13 out of 10,000 on high-volume days and 15 out of 10,000 on low-volume or average-volume days; P=.182). The cesarean delivery rate among the nulliparous, term, singleton, vertex population was significantly lower on high-volume weekend days (22.0% compared with 23.6% on low-volume or average-volume weekend days; P=.009), whereas no association was present on weekdays (27.1% on high-volume days and 27.6% on low-volume or average-volume days; P=.092).

CONCLUSION: Delivery on relatively high-volume weekend days is a risk factor for birth asphyxia in California. High-volume weekend days also are associated with a lower rate of cesarean delivery in nulliparous women with singleton, vertex presentation pregnancies at term.


Delivery on high-volume weekend days is associated with increased risk of birth asphyxia and a decreased nulliparous, term, singleton, vertex cesarean delivery rate.

Departments of Obstetrics and Gynecology, Medical Informatics and Clinical Epidemiology, and Emergency Medicine, and the Center for Health Systems Effectiveness, Oregon Health and Science University, Portland, Oregon; and the Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California.

Corresponding author: Jonathan M. Snowden, PhD, Department of Obstetrics and Gynecology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code L466, Portland, OR 97209; e-mail:

Dr. Snowden and Dr. Caughey are supported by grant R40 MC 25694-01-00 from the Maternal and Child Health Research Program, Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Services Administration, Department of Health and Human Services. Dr. Cheng is supported by the University of California San Francisco Women's Reproductive Health Research Career Development Award, National Institutes of Health, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (K12 HD001262). Dr. Darney is supported by an AHRQ postdoctoral award (T32 HS017582).

Financial Disclosure The authors did not report any potential conflicts of interest.

© 2013 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.