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Comparing variation in hospital rates of cesarean delivery among low-risk women using 3 different measures

Published:November 16, 2015DOI:https://doi.org/10.1016/j.ajog.2015.10.935
      This report describes the development of a measure of low-risk cesarean delivery by the Society for Maternal-Fetal Medicine (SMFM). Safely lowering the cesarean delivery rate is a priority for maternity care clinicians and health care delivery systems. Therefore, hospital quality assurance programs are increasingly tracking cesarean delivery rates among low-risk pregnancies. Two commonly used definitions of “low risk” are available, the Joint Commission (JC) and the Agency for Healthcare Research and Quality (AHRQ) measures, but these measures are not clinically comprehensive. We sought to refine the definition of the low-risk cesarean delivery rate to enhance the validity of the metric for quality measurement. We created this refined definition–called the SMFM definition–and compared it to the JC and AHRQ measures using claims-based data from the 2011 Nationwide Inpatient Sample of >863,000 births in 612 hospitals. Using these definitions, we calculated means and interquartile ranges (25th-75th percentile range) for hospital low-risk cesarean delivery rates, stratified by hospital size, teaching status, urban/rural location, and payer mix. Across all hospitals, the mean low-risk cesarean delivery rate was lowest for the SMFM definition (12.65%), but not substantially different from the JC and AHRQ measures (13.12% and 13.29%, respectively). We empirically examined the SMFM definition to ensure its validity and utility. This refined definition performs similarly to existing measures and has the added advantage of clinical perspective, enhanced face validity, and ease of use.

      Key words

      Members of the Society for Maternal-Fetal Medicine Health Policy Committee: Joanne Armstrong, Sean C. Blackwell, Suneet P. Chauhan, Rebekah Gee, William Grobman, James Keller, Judette Louis, Kate Menard, Dan O’Keeffe, Carolina Reyes, George R. Saade, Kathryn Schubert, Cathy Spong, Sindhu Srinivas, and Thomas Westover.

      Measurement of the low-risk cesarean delivery rate

      Lowering the low-risk cesarean delivery rate has been a recent public health focus.

      US Department of Health and Human Services. Office of Disease Prevention and Health Promotion. Healthy people 2020. Washington (DC). Available at: http://www.healthypeople.gov/2020/topics-objectives/topic/maternal-infant-and-child-health/objectives. Accessed May 15, 2015.

      • Spong C.Y.
      • Berghella V.
      • Wenstrom K.D.
      • Mercer B.M.
      • Saade G.R.
      Preventing the first cesarean delivery: summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists workshop.
      American College of Obstetrics and Gynecology; Society for Maternal-Fetal Medicine
      Safe prevention of the primary cesarean delivery. Obstetric care consensus no. 1.
      Two risk-adjusted or low-risk cesarean delivery rate measures developed by the Joint Commission (JC) and the Agency for Healthcare Research and Quality (AHRQ) are currently used for hospital reporting.

      Joint Commission. Measure information form PC-02 cesarean section rate. Perinatal care core measure set. Specifications manual for Joint Commission national quality measures (v2015A1). Available at: https://manual.jointcommission.org/releases/TJC2015A1/MIF0167.html. Accessed May 15, 2015.

      Agency for Healthcare Research and Quality (AHRQ) National Quality Measures Clearinghouse. Primary cesarean delivery rate, uncomplicated (IQI 33). HHS:005884. Available at: http://www.qualitymeasures.ahrq.gov/hhs/content.aspx?id=46105. Accessed May 15, 2015.

      Both define “low risk” as term, singleton, live birth deliveries in the vertex presentation. The JC measure applies only to nulliparous patients. The AHRQ measure captures women with no prior cesareans. Both measures identify additional medical factors that classify the delivery as high risk for cesarean delivery and thus exclude those deliveries from measurement (Table 1). The medical factors identified for exclusion are similar, but not identical, between the 2 measures. Further, these lists are not exhaustive, omitting some well-accepted contraindications to vaginal birth such as placenta previa as well as conditions that are likely to lead to cesarean delivery such as HIV infection. Although these risk factors have low prevalence at a population level, if they are not excluded in a low-risk cesarean delivery rate definition, the face validity of the measure for practicing physicians and hospitals is decreased. Further, this creates skepticism about the measure, particularly among hospitals that disproportionately care for women with some of these conditions. More concerning from a policy perspective is the potential of limiting access to care to women with high-risk conditions that are not excluded from the low-risk cesarean delivery definition as a strategy to reduce the low-risk cesarean delivery rate. An additional challenge with the JC measure is that it is labor intensive and requires hospital resources for chart abstraction.
      Table 1ICD-9 codes indicating medical exclusion conditions for cesarean rate calculations according to 3 definitions
      ICD9 Diagnosis CodeICD9 Diagnosis Code Short DescriptionRisk Factor ClassificationSMFMJCAHRQ
      042HUMAN IMMUNO VIRUS DISMaternal factorsx
      641.01PLACENTA PREVIA-DELIVERMaternal factorsx
      641.11PLACENTA PREV HEM-DELIVMaternal factorsx
      642.6ECLAMPSIAMaternal factorsx
      642.60ECLAMPSIA-UNSPECIFIEDMaternal factorsx
      642.61ECLAMPSIA-DELIVEREDMaternal factorsx
      642.62ECLAMPSIA-DELIV W P/PMaternal factorsx
      642.63ECLAMPSIA-ANTEPARTUMMaternal factorsx
      644.2EARLY ONSET OF DELIVERYPreterm birthx
      644.20EARLY ONSET DELIV-UNSPECPreterm birthxX
      644.21EARLY ONSET DELIVERY-DELPreterm birthxxx
      646PAPYRACEOUS FETUSStillbornx
      646.0PAPYRACEOUS FETUSStillbornx
      646.00PAPYRACEOUS FETUS-UNSPECStillbornx
      646.01PAPYRACEOUS FETUS-DELIVStillbornx
      646.03PAPYRACEOUS FET-ANTEPARStillbornx
      648.51CONGEN CV DIS-DELIVEREDMaternal factorsx
      648.52CONGEN CV DIS-DEL W P/PMaternal factorsx
      648.53CONGEN CV DIS-ANTEPARTUMMaternal factorsx
      648.54CONGEN CV DIS-POSTPARTUMMaternal factorsx
      648.6OTHER CARDIOVASCULAR DISEASEMaternal factorsx
      648.60CV DIS NEC PREG-UNSPECMaternal factorsx
      648.61CV DIS NEC PREG-DELIVERMaternal factorsx
      648.62CV DIS NEC-DELIVER W P/PMaternal factorsx
      648.63CV DIS NEC-ANTEPARTUMMaternal factorsx
      648.64CV DIS NEC-POSTPARTUMMaternal factorsx
      651TWIN PREGNANCYMultiple gestationx
      651.0TWIN PREGNANCYMultiple gestationx
      651.00TWIN PREGNANCY-UNSPECMultiple gestationxx
      651.01TWIN PREGNANCY-DELIVEREDMultiple gestationxxx
      651.03TWIN PREGNANCY-ANTEPARTMultiple gestationxx
      651.1TRIPLET PREGNANCYMultiple gestationx
      651.10TRIPLET PREGNANCY-UNSPECMultiple gestationxx
      651.11TRIPLET PREGNANCY-DELIVMultiple gestationxxx
      651.13TRIPLET PREG-ANTEPARTUMMultiple gestationxx
      651.2QUADRUPLET PREGNANCYMultiple gestationx
      651.20QUADRUPLET PREG-UNSPECMultiple gestationxx
      651.21QUADRUPLET PREG-DELIVERMultiple gestationxxx
      651.23QUADRUPLET PREG-ANTEPARTMultiple gestationxx
      651.3TWIN PREGNANCY WITH FETAL LOMultiple gestationx
      651.30TWINS W FETAL LOSS-UNSPMultiple gestationxx
      651.31TWINS W FETAL LOSS-DELMultiple gestationxxx
      651.33TWINS W FETAL LOSS-ANTEMultiple gestationxx
      651.4TRIPLET PREGNANCY WITH FETALMultiple gestationx
      651.40TRIPLETS W FET LOSS-UNSPMultiple gestationxx
      651.41TRIPLETS W FET LOSS-DELMultiple gestationxxx
      651.43TRIPLETS W FET LOSS-ANTEMultiple gestationxx
      651.5QUADRUPLET PREGNANCY WITH FEMultiple gestationx
      651.50QUADS W FETAL LOSS-UNSPMultiple gestationxx
      651.51QUADS W FETAL LOSS-DELMultiple gestationxxx
      651.53QUADS W FETAL LOSS-ANTEMultiple gestationxx
      651.6OTHER MULTIPLE PREGNANCY WITMultiple gestationx
      651.60MULT GES W FET LOSS-UNSPMultiple gestationxx
      651.61MULT GES W FET LOSS-DELMultiple gestationxxx
      651.63MULT GES W FET LOSS-ANTEMultiple gestationxx
      651.7MULTIPLE GESTATIONMultiple gestationx
      651.70MUL GEST-FET REDUCT UNSPMultiple gestationx
      651.71MULT GEST-FET REDUCT DELMultiple gestationx
      651.73MUL GEST-FET REDUCT ANTEMultiple gestationx
      651.8OTHER SPECIFIED MULTIPLE GESMultiple gestationx
      651.80MULTI GESTAT NEC-UNSPECMultiple gestationxx
      651.81MULTI GESTAT NEC-DELIVERMultiple gestationxxx
      651.83MULTI GEST NEC-ANTEPARTMultiple gestationxx
      651.9UNSPECIFIED MULTIPLE GESTATIMultiple gestationx
      651.90MULTI GESTAT NOS-UNSPECMultiple gestationxx
      651.91MULT GESTATION NOS-DELIVMultiple gestationxxx
      651.93MULTI GEST NOS-ANTEPARTMultiple gestationxx
      652.20BREECH PRESENTAT-UNSPECMalpresentationx
      652.21BREECH PRESENTAT-DELIVERMalpresentationxxx
      652.23BREECH PRESENT-ANTEPARTMalpresentationx
      652.30TRANSV/OBLIQ LIE-UNSPECMalpresentationx
      652.31TRANSVER/OBLIQ LIE-DELIVMalpresentationxxx
      652.33TRANSV/OBLIQ LIE-ANTEPARMalpresentationx
      652.40FACE/BROW PRESENT-UNSPECMalpresentationx
      652.41FACE/BROW PRESENT-DELIVMalpresentationxxx
      652.43FACE/BROW PRES-ANTEPARTMalpresentationx
      652.6MULTIPLE GESTATION, MALPRESEMultiple gestationx
      652.60MULT GEST MALPRESEN-UNSPMultiple gestationxx
      652.61MULT GEST MALPRES-DELIVMultiple gestationxxx
      652.63MULT GES MALPRES-ANTEPARMultiple gestationxx
      652.70PROLAPSED ARM-UNSPECMalpresentationx
      652.71PROLAPSED ARM-DELIVEREDMalpresentationx
      652.81MALPOSITION NEC-DELIVERMalpresentationx
      653.6HYDROCEPHALIC FETUS CAUSINGFetal factorsx
      653.60HYDROCEPHAL FETUS-UNSPECFetal factorsx
      653.61HYDROCEPH FETUS-DELIVERFetal factorsx
      653.63HYDROCEPH FETUS-ANTEPARTFetal factorsx
      653.71OTH ABN FET DISPRO-DELIVFetal factorsx
      654.2UTERINE SCAR FROM PREVIOUS SUterine/placental factorsx
      654.20PREV C-DELIVERY UNSPECUterine/placental factorsxx
      654.21PREV C-DELIVERY-DELIVRDUterine/placental factorsxxx
      654.23PREV C-DELIVERY-ANTEPARTUterine/placental factorsxx
      654.3RETROVERTED AND INCARCERATEDUterine/placental factorsx
      654.30RETROVERT UTERUS-UNSPECUterine/placental factorsx
      654.31RETROVERT UTERUS-DELIVERUterine/placental factorsx
      654.32RETROVERT UTER-DEL W P/PUterine/placental factorsx
      654.33RETROVERT UTER-ANTEPARTUterine/placental factorsx
      654.34RETROVERT UTER-POSTPARTUterine/placental factorsx
      655.01FETAL CNS MALFORM-DELIVFetal factorsx
      656.4INTRAUTERINE DEATH COMPLICATStillbornx
      656.40INTRAUTERINE DEATH-UNSPStillbornxxx
      656.41INTRAUTER DEATH-DELIVERStillbornxxx
      656.43INTRAUTER DEATH-ANTEPARTStillbornx
      660.3DEEP TRANSVERSE ARREST, PERSMalpresentationx
      660.30DEEP TRANS ARR AND PERSIST OP-UNSPMalpresentationx
      660.31DEEP TRANS ARR AND PERSIST OP -DELIVMalpresentationx
      660.5LOCKED TWINS COMPLICATING PRMultiple gestationx
      660.50LOCKED TWINS-UNSPECIFIEDMultiple gestationxx
      660.51LOCKED TWINS-DELIVEREDMultiple gestationxxx
      660.53LOCKED TWINS-ANTEPARTUMMultiple gestationxx
      660.7FAILED FORCEPS OR VACUUM EXTConduct of laborx
      660.70FAILED FORCEP NOS-UNSPECConduct of laborx
      660.71FAILED FORCEPS NOS-DELIVConduct of laborx
      660.73FAIL FORCEPS NOS-ANTEPARConduct of laborx
      662.3DELAYED DELIVERY SECOND TWINMultiple gestationx
      662.30DELAY DEL 2ND TWIN-UNSPMultiple gestationxx
      662.31DELAY DEL 2ND TWIN-DELIVMultiple gestationxxx
      662.33DELAY DEL 2 TWIN-ANTEPARMultiple gestationxx
      663PROLAPSE OF UMBILICAL CORD CUterine/placental factorsx
      663.0PROLAPSE OF UMBILICAL CORD CUterine/placental factorsx
      663.00CORD PROLAPSE-UNSPECUterine/placental factorsx
      663.01CORD PROLAPSE-DELIVEREDUterine/placental factorsx
      663.03CORD PROLAPSE-ANTEPARTUMUterine/placental factorsx
      663.5VASA PREVIA COMPLICATING PREUterine/placental factorsx
      663.50VASA PREVIA-UNSPECIFIEDUterine/placental factorsx
      663.51VASA PREVIA-DELIVEREDUterine/placental factorsx
      663.53VASA PREVIA-ANTEPARTUMUterine/placental factorsx
      665RUPTURE UTERUS BEFORE ONSETUterine/placental factorsx
      665.0RUPTURE UTERUS BEFORE ONSETUterine/placental factorsx
      665.00PRELABOR RUPT UTER-UNSPUterine/placental factorsx
      665.01PRELABOR RUPT UTERUS-DELUterine/placental factorsx
      665.03PRELAB RUPT UTER-ANTEPARUterine/placental factorsx
      665.1RUPTURE UTERUS DURING/AFTERUterine/placental factorsx
      665.10RUPTURE UTERUS NOS-UNSPUterine/placental factorsx
      665.11RUPTURE UTERUS NOS-DELIVUterine/placental factorsx
      665.12RUPTURE UTERUS DURING/AFTERUterine/placental factorsx
      665.14RUPTURE UTERUS DURING/AFTERUterine/placental factorsx
      669.6BREECH EXTRACTION WITHOUT MEMalpresentationx
      669.60BREECH EXTR NOS-UNSPECMalpresentationxx
      669.61BREECH EXTR NOS-DELIVERMalpresentationxxx
      678.10FETAL CONJOIN TWINS-UNSPFetal factorsxx
      678.11FETAL CONJOIN TWINS-DELFetal factorsxx
      678.13FETAL CONJOIN TWINS-ANTEFetal factorsxx
      761.5MULT PREGNANCY AFF NBMultiple gestationxxx
      V08ASYMP HIV INFECTN STATUSMaternal factorsx
      V27.1DELIVER-SINGLE STILLBORNStillbornxxx
      V27.2DELIVER-TWINS, BOTH LIVEMultiple gestationxxx
      V27.3DEL-TWINS, 1 NB, 1 SBStillbornxxx
      V27.4DELIVER-TWINS, BOTH SBStillbornxxx
      V27.5DEL-MULT BIRTH, ALL LIVEMultiple gestationxxx
      V27.6DEL-MULT BRTH, SOME LIVEMultiple gestationxxx
      V27.7DEL-MULT BIRTH, ALL SBStillbornxxx
      V91.00TWIN GEST-PLAC/SAC NOSMultiple gestationx
      V91.01TWIN GEST-MONOCHR/MONOAMMultiple gestationx
      V91.02TWIN GEST-MONOCHR/DIAMNIMultiple gestationx
      V91.03TWIN GEST-DICH/DIAMNIOTCMultiple gestationx
      V91.09TWIN GEST-PLAC/SAC UNDETMultiple gestationx
      V91.10TRIPL GEST-PLAC/SAC NOSMultiple gestationx
      V91.11TRIPLET GEST 2+ MONOCHORMultiple gestationx
      V91.12TRIPLET GEST 2+ MONOAMNMultiple gestationx
      V91.19TRIPL GEST-PLAC/SAC UNDMultiple gestationx
      V91.20QUAD GEST-PLAC/SAC NOSMultiple gestationx
      V91.21QUAD GEST 2+ MONOCHORIONMultiple gestationx
      V91.22QUAD GEST 2+ MONOAMNIOTCMultiple gestationx
      V91.29QUAD GEST-PLAC/SAC UNDETMultiple gestationx
      V91.90MULT GEST-PLAC/SAC NOSMultiple gestationx
      V91.91MULT GEST 2+ MONOCHR NECMultiple gestationx
      V91.92MULT GEST 2+ MONOAMN NECMultiple gestationx
      V91.99MULT GEST-PLAC/SAC UNDETMultiple gestationx
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.
      The availability of a published, risk-adjusted cesarean delivery rate measure based on a comprehensive list of clinically valid diagnoses that are easily identified in administrative data is therefore needed to facilitate adoption by the clinical community and allow comparisons of quality and variation among hospitals. We sought to extend the efforts of the Society for Maternal-Fetal Medicine (SMFM) in this arena and to refine the definition of the low-risk cesarean delivery rate by building on the 2 previous measures and excluding additional clinically relevant risk factors. We then compared the performance of this refined definition to the JC and AHRQ measures in a nationally representative sample of US hospitals. The new definition was developed with the assistance of maternal-fetal medicine specialists and is supported by the SMFM Coding and Health Policy Committees giving it additional credibility among practicing clinicians.

      Development and testing of a refined definition

      Hospital discharge data were used in a retrospective analysis of hospital cesarean rates, based on 3 different measures, 2 established measures (JC and AHRQ) compared with a newly proposed measure based on a more comprehensive inclusion of clinical risk factors and developed by the SMFM. This measure will be referred to as the SMFM measure for the remainder of the article.

      Data and study population

      Data from the 2011 Nationwide Inpatient Sample (NIS), Healthcare Cost and Utilization Project, AHRQ were analyzed. The NIS is an all-payer inpatient claims database designed to approximate a 20% stratified sample of US hospitals.

      Agency for Healthcare Research and Quality. Introduction to the HCUP nationwide inpatient sample (NIS). Rockville (MD). Available at: http://www.hcup-us.ahrq.gov. Accessed Jan 28, 2015.

      Nationwide Inpatient Sample, Health Care Cost and Utilization Project, Agency for Healthcare Research and Quality. Database documentation. Available at: http://www.hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp. Accessed Jan 28, 2015.

      While it contains only administrative data, not clinical information, it is one of the most comprehensive national sources of information on hospital-based care in the United States. Hospitals represented in the NIS data include all US hospitals (nonfederal, short-term, general, and other specialty hospitals, including obstetrics gynecology, ear-nose-throat, orthopedic, and pediatric institutions). This includes both public hospitals and academic medical centers. Detailed information on the NIS data set, methodology, and variables is publicly available.

      HCUP Databases. Healthcare Cost and Utilization Project (HCUP). Agency for Healthcare Research and Quality, Rockville, MD. Available at: http://www.hcup-us.ahrq.gov/databases.jsp. Accessed December 10, 2015.

      Our analyses focused on hospitals that reported discharges with neonatal and/or maternal diagnoses and procedures. From these hospitals, we used a validated methodology to identify hospital discharge records for obstetric deliveries in 2011.
      • Kuklina E.V.
      • Whiteman M.K.
      • Hillis S.D.
      • et al.
      An enhanced method for identifying obstetric deliveries: implications for estimating maternal morbidity.
      We excluded hospitals with <100 births, consistent with prior research, to ensure enough sample for cross-hospital comparisons.
      • Kozhimannil K.B.
      • Law M.R.
      • Virnig B.A.
      Cesarean delivery rates vary ten-fold among US hospitals; reducing variation may address quality and cost issues.
      Our final data set included 863,346 births in 612 hospitals in 46 states.

      Medical exclusions for refined cesarean rate calculations

      A refined measure of the risk-adjusted cesarean delivery rate, or low-risk definition was created. It included all term, singleton, vertex, live birth deliveries without prior cesarean and without high-risk diagnoses. Women with prior cesarean deliveries were excluded given the practice variation in trial of labor after cesarean delivery and the impact of patient choice on this decision. Initially, each diagnosis code was reviewed and classified independently by 2 authors (S.K.S. and J.C.A.) for inclusion in the measure. This was performed through systematic review and classification of all diagnoses codes in the International Classification of Diseases, Ninth Revision (ICD-9) in the maternity code range of 641.00 through 669.6, V22 through V28.9, and V91.00 through V91.99.

      ICD-9-CM: International classification of diseases, 9th revision, clinical modification. 1996. Salt Lake City, Utah: Medicode.

      In our classification, we followed the practice guidelines of the American Congress of Obstetricians and Gynecologists (ACOG) or the SMFM as much as possible.
      American College of Obstetrics and Gynecology; Society for Maternal-Fetal Medicine
      Safe prevention of the primary cesarean delivery. Obstetric care consensus no. 1.

      American Academy of Pediatrics, American College of Obstetricians and Gynecologists. Guidelines for perinatal care. 7th ed. Elk Grove Village (IL): American Academy of Pediatrics; Washington (DC): American College of Obstetricians and Gynecologists; 2012.

      American College of Obstetricians and Gynecologists
      2015 Compendium of selected publications [CD-Rom].
      In the absence of a practice guideline, clinical expertise was used to determine conditions to be excluded from the low-risk definition based on the following principles: obstetric risk factors had to be present prior to delivery or in the intrapartum course (not a postpartum occurrence); maternal conditions where vaginal delivery may be relatively contraindicated (eg, maternal cardiac disease); obstetric clinical factors where there is a contraindication to vaginal delivery or broad professional acceptance of cesarean delivery (eg, umbilical cord prolapse). Of note, most progress of labor disorders (with some exceptions) are not classified as high risk due to the discretionary/subjective nature of labor management. The clinical conditions classified as high risk and thus excluded from the SMFM measure were in addition to those already excluded in the JC and AHRQ measures. In no case was a clinical condition identified as high risk in the JC and AHRQ measures reclassified as low risk in the SMFM measure. The final code list (Table 1) was reviewed and supported by the coding committee of the SMFM.

      Variable measurement

      We identified cesarean delivery using ICD-9 procedure codes (740X, 741X, 742X, 744X, 7499) as well as Diagnosis Related Group payment codes (370, 371), consistent with validated methods and prior research using the NIS data.
      • Kuklina E.V.
      • Whiteman M.K.
      • Hillis S.D.
      • et al.
      An enhanced method for identifying obstetric deliveries: implications for estimating maternal morbidity.
      We calculated each hospital’s cesarean delivery rate as the percentage of cesareans among obstetric deliveries to all women who met the criteria for low risk according to each of the 3 definitions: the JC perinatal care core measure PC-02, AHRQ inpatient quality indicator no. 33, and the newly defined measure by SMFM described above.
      The JC measure is defined based on the Specifications Manual for JC National Quality Measures (v2015A1, Appendix A).

      Joint Commission. Measure information form PC-02 cesarean section rate. Perinatal care core measure set. Specifications manual for Joint Commission national quality measures (v2015A1). Available at: https://manual.jointcommission.org/releases/TJC2015A1/MIF0167.html. Accessed May 15, 2015.

      Contraindications for vaginal delivery included complications related to preterm labor or multiple gestation, long or obstructed labor with multiple gestation, malpresentation (eg, breech), complications from prior cesareans, and other serious fetal or placental problems. Parity is not specified by ICD-9 codes and is therefore not distinguished in the JC measure as specified in the definition of PC-02 cesarean delivery, however women with prior cesarean deliveries are excluded. The AHRQ measure is defined based on the specifications outlined in the National Quality Measures Clearinghouse and excludes deliveries with complications including abnormal presentation, preterm delivery, fetal death, multiple gestation diagnosis, or breech presentation.

      Agency for Healthcare Research and Quality (AHRQ) National Quality Measures Clearinghouse. Primary cesarean delivery rate, uncomplicated (IQI 33). HHS:005884. Available at: http://www.qualitymeasures.ahrq.gov/hhs/content.aspx?id=46105. Accessed May 15, 2015.

      Women are excluded from the denominators of these risk-adjusted or low-risk hospital cesarean rate measures on the basis of the ICD-9 diagnosis and procedure codes described in these measures and listed in Table 1. All patient-level measures are based on administrative records, ICD-9 diagnosis and procedure codes, and Clinical Classification Software (Healthcare Cost and Utilization Project, Rockville, MD) codes, developed for use with ICD-9 codes.
      We used a unique hospital identification code to group deliveries by hospital. We also used hospital-specific data on bed size, teaching status, birth volume (100-500, 501-1000, and ≥1000), and rural vs urban location. Bed size was defined as small, medium, or large based on AHRQ methodology.

      HCUP NIS Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). September 2008. Agency for Healthcare Research and Quality, Rockville, MD. Available at: http://www.hcup-us.ahrq.gov/db/vars/hosp_bedsize/nisnote.jsp. Accessed December 10, 2015.

      Hospital teaching status was based on information from the American Hospital Association’s Annual Survey of Hospitals. Classification of hospitals as either urban or rural was based on core-based statistical area codes from Census 2000 data. Based on patient-level information on primary payer (private insurance, Medicare, Medicaid, self-pay/uninsured, or other), we also created a measure of a hospital’s payer mix, which was categorized as predominantly commercial if >50% of a hospital’s 2011 births had private insurance listed as the primary payer and predominantly public if private insurance financed fewer than half of births in that hospital.

      Analysis

      We report descriptive statistics and calculated hospital rates of cesarean delivery, according to 2 established and 1 new measure for cesarean delivery rates for all hospitals and stratified by hospital bed size, teaching status, geographic location, and payer mix. For each stratum, we calculated the minimum, maximum, and mean number of deliveries as well as the interquartile ranges (IQRs) (the difference between the 25th and 75th percentiles). The IQR provides a measure of the variability of hospital rates across facilities within that stratum. Higher IQRs indicate greater variability.
      In addition, we assessed cesarean rates across the 3 measures for each individual hospital and calculated the percentage of hospitals for which low-risk cesarean rates were lower using the SMFM measure, compared with both the JC and AHRQ measures. We also calculated comparisons for 3 subgroups of hospitals: (1) all large, urban, teaching hospitals with primarily public payers; (2) all large, urban, nonteaching hospitals with primarily private payers; and (3) all medium, rural, nonteaching hospitals with primarily public payers. Finally, we plotted cesarean rates, based on measures comparisons. Data for this analysis were deidentified, and as such, the study was granted exemption from review by the University of Minnesota Institutional Review Board (study number 1011E92980).

      Performance and comparison of the SMFM definition

      As can be seen in Table 1, many conditions that are likely to lead to cesarean delivery were not included in the low-risk exclusion for the JC and AHRQ definitions. Characteristics of the hospitals in the sample are shown in Table 2. The mean number of births among the 612 hospitals was 1410, and the median number was 851. A quarter of the hospitals were urban teaching hospitals, and 43% were urban nonteaching hospitals, while 32% were rural nonteaching hospitals. Nearly half of the hospitals were large or had >1000 births annually (46% and 44%, respectively). Almost 40% of hospitals had a predominantly commercial payer mix, with the remaining 61% of hospitals having more than half of births financed by public programs or individual payers.
      Table 2Hospital Characteristics
      Number of hospitals with over 100 births612
      Total deliveries8,63,346
      Mean number births per hospital1410
      Median number of births per hospital851
      Teaching status and location
      Hospital teaching status was obtained by HCUP from the AHA Annual Survey of Hospitals
      Teaching (urban
      Classification of urban or rural hospital location used Core Based Statistical Area (CBSA) codes based on 2000 Census data; prior to 2004 Metropolitan Statistical Area (MSA) was used. Hospitals residing in counties with a CBSA or MSA type of metropolitan were considered urban, while hospitals with a CBSA or MSA type of micropolitan or non-core were classified as rural
      )
      152 (25%)
      Non-teaching (urban)259 (43%)
      Non-teaching (rural)194 (32%)
      Bed size
      Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size.
      Small136 (22%)
      Medium192 (32%)
      Large277 (46%)
      Birth volume
      100-500 deliveries annually215 (35%)
      501 – 1000 deliveries annually127 (21%)
      1001+ deliveries annually270 (44%)
      Payer mix
      Predominantly private payers (>50% of deliveries)239 (39%)
      Predominantly non-private (public or individual) payers ( >50 % of deliveries)373 (61%)
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.
      a Hospital teaching status was obtained by HCUP from the AHA Annual Survey of Hospitals
      b Classification of urban or rural hospital location used Core Based Statistical Area (CBSA) codes based on 2000 Census data; prior to 2004 Metropolitan Statistical Area (MSA) was used. Hospitals residing in counties with a CBSA or MSA type of metropolitan were considered urban, while hospitals with a CBSA or MSA type of micropolitan or non-core were classified as rural
      c Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size.
      The mean and range of hospital birth volume varied by hospital size, teaching status, and rural/urban location, but not payer mix (Table 3). Across all hospitals, the mean hospital low-risk cesarean rate was lowest for the SMFM measure (12.65%), but very similar for both the JC and AHRQ measures (13.12% and 13.29%, respectively). Average rates varied slightly across hospital strata, with rates being higher, in general, for teaching hospitals (16.24%, 16.58%, 16.71%) and lower, in general, for rural hospitals (10.86%, 11.41%, 11.58%). However, the average rates were similar across measures within each strata. The magnitude of the variability of cesarean rates across strata (as measured by the IQR) is similar for all 3 cesarean rate measures.
      Table 3Mean values and range of low-risk cesarean rates in U.S. hospitals with >100 births in 2011, overall and stratified by size, teaching status, and location (N=612)
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.
      All hospitalsSmall hospitals
      IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      The low-risk cesarean rate is calculated as the percentage of cesarean deliveries among women with term, singleton, vertex pregnancies and no prior history of cesarean section
      Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size
      Medium hospitals
      Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size
      Large hospitals
      Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size
      Teaching hospitals
      Hospital teaching status was obtained by HCUP from the AHA Annual Survey of Hospitals
      Non-teaching hospitlas
      Hospital teaching status was obtained by HCUP from the AHA Annual Survey of Hospitals
      Rural hospitals
      Classification of urban or rural hospital location used Core Based Statistical Area (CBSA) codes based on 2000 Census data; prior to 2004 Metropolitan Statistical Area (MSA) was used. Hospitals residing in counties with a CBSA or MSA type of metropolitan were considered urban, while hospitals with a CBSA or MSA type of micropolitan or non-core were classified as rural.
      Urban hospitals
      Classification of urban or rural hospital location used Core Based Statistical Area (CBSA) codes based on 2000 Census data; prior to 2004 Metropolitan Statistical Area (MSA) was used. Hospitals residing in counties with a CBSA or MSA type of metropolitan were considered urban, while hospitals with a CBSA or MSA type of micropolitan or non-core were classified as rural.
      Predominantly public or individual payers (>50% of births)Predominantly private payers (>50% births)
      N=612N=136N=192N=277N=159N=446n=194n=411n=373n=239
      Number of obstetric deliveries
      Mean14106671,1041,9772,620973455185412141718
      Min101101107110107101102101102101
      Max13,9994,4148,84913,99913,9996,1971,98113,99913,99913,657
      IQR
      IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      1,5308111,1272,1042,1649123691,8281,1711,840
      % of low-risk women (SMFM definition) with cesarean delivery
      The low-risk cesarean rate is calculated as the percentage of cesarean deliveries among women with term, singleton, vertex pregnancies and no prior history of cesarean section
      Mean12.65113.14913.19912.08516.24311.40610.86413.53412.69312.587
      IQR
      IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      5.9597.2856.2875.3426.9625.936.6196.0315.9465.752
      % of low-risk women (Joint Commission) with cesarean delivery
      The low-risk cesarean rate is calculated as the percentage of cesarean deliveries among women with term, singleton, vertex pregnancies and no prior history of cesarean section
      Mean13.12313.75713.73312.45216.57711.93111.40713.97513.11713.133
      IQR
      IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      6.0756.7746.9375.196.5835.9576.0966.0346.0976.004
      % of low-risk women (AHRQ definition) with cesarean delivery
      The low-risk cesarean rate is calculated as the percentage of cesarean deliveries among women with term, singleton, vertex pregnancies and no prior history of cesarean section
      Mean13.29413.91113.91312.62216.71312.11211.58314.14213.313.285
      IQR
      IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      6.0077.0936.7985.4386.8155.8186.0656.1946.285.76
      a IQR is the interquartile range, a measure of variability, calculated as the difference between the 75th and 25th percentiles. Larger numbers indicate greater variability across hospitals within a column
      b The low-risk cesarean rate is calculated as the percentage of cesarean deliveries among women with term, singleton, vertex pregnancies and no prior history of cesarean section
      c Hospital bed size categories are defined by the Healthcare Cost and Utilization Project (HCUP), based on number of short-term acute hospital beds, and are specific to the hospital's U.S. region, rural-urban designation, and teaching status. Thirteen hospitals are missing information for bed size
      d Hospital teaching status was obtained by HCUP from the AHA Annual Survey of Hospitals
      e Classification of urban or rural hospital location used Core Based Statistical Area (CBSA) codes based on 2000 Census data; prior to 2004 Metropolitan Statistical Area (MSA) was used. Hospitals residing in counties with a CBSA or MSA type of metropolitan were considered urban, while hospitals with a CBSA or MSA type of micropolitan or non-core were classified as rural.
      Among all 612 hospitals in the sample, 484 (79.1%) had a lower rate of cesarean delivery in low-risk women based on the SMFM measure compared with the JC measure (Table 4). More than 90% (n = 563) of hospitals had a lower rate using the SMFM measure compared with the AHRQ measure. Results were similar when looking at specific subgroups of hospitals. Among large, urban teaching hospitals with primarily noncommercial payers (n = 41), 78.0% and 90.2% had lower low-risk cesarean rates with the SMFM measure compared with the JC and AHRQ measures, respectively. Similarly, all 49 large, urban nonteaching hospitals with primarily private payers had lower low-risk cesarean delivery rates using the SMFM compared with the AHRQ measure, and 81.6% had a lower rate compared with the JC measure. Finally, among medium, rural, nonteaching hospitals with primarily noncommercial payers, >75% of hospitals had a lower rate under SMFM than JC and AHRQ measures.
      Table 4Number and percentage of hospitals with lower cesarean rates using the SMFM-proposed measure, compared with Joint Commission and AHRQ measures
      Lower cesarean rate with SMFM measure, compared with Joint Commission measureLower cesarean rate with SMFM measure, compared with AHRQ measure
      N (%)N (%)
      All hospitals (N=612)484 (79.1)563 (92.0)
      All large, urban, teaching hospitals with primarily public payers (N=41)32 (78.0)37 (90.2)
      All large, urban, non-teaching hospitals with primarily private payers (N=49)40 (81.6)49 (100.0)
      All medium, rural, non-teaching hospitals with primarily public payers (N=42)31 (73.8)37 (88.1)
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.
      Figures 1 and 2 represent the plot for each hospital’s low-risk cesarean rate according to the SMFM definition (y-axis) vs either the JC definition (x-axis, Figure 1) or AHRQ definition (x-axis, Figure 2). Each point represents 1 hospital, and points located below or to the right of the diagonal line represent a hospital with a lower cesarean rate, when measured using the SMFM definition, compared with the other 2 definitions. Consistent with results reported in Table 4, Figures 1 and 2 indicate that risk adjustment using the SMFM measure resulted in lower low-risk cesarean rates at the hospital level, in general and for the vast majority of individual hospitals, compared with other established measures.
      Figure thumbnail gr1
      Figure 1Hospital low-risk cesarean rates, comparing SMFM and JC definitions
      Individual hospital low-risk cesarean rates, Society for Maternal-Fetal Medicine (SMFM) definition compared with Joint Commission definition (all hospitals, n = 612).
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.
      Figure thumbnail gr2
      Figure 2Hospital low-risk cesarean rates, comparing SMFM and AHRQ definitions
      Individual hospital low-risk cesarean rates, Society for Maternal-Fetal Medicine (SMFM) definition compared with Agency for Healthcare Research and Quality (AHRQ) definition (all hospitals, n = 612).
      Armstrong. Hospital rates of cesarean delivery among low-risk women. Am J Obstet Gynecol 2016.

      The value of the SMFM definition in quality measurement

      After a persistent rise in the total cesarean delivery rate over the past decades, there is now broad interest in safely lowering the rate. Multiple factors have contributed to the rise in the cesarean delivery rate, including nonmedical factors, labor management and induction practices, changes in the prevalence of medical risk factors, and medicolegal concerns. A number of discretionary practice behaviors that unintentionally contributed to the increase in the rate have been the focus of policy changes at the hospital and/or professional college level. For example, the practice of eliminating elective deliveries <39 weeks’ gestation has enjoyed broad physician support with dramatic reductions in the practice over a few years.
      • Oshiro B.T.
      • Kowalewski L.
      • Sappenfield W.
      • et al.
      A multistate quality improvement program to decrease elective deliveries before 39 weeks of gestation.
      More recently, ACOG and SMFM have issued obstetric care consensus guidelines on labor arrest management with an aim to safely reduce the primary cesarean delivery rate.
      • Spong C.Y.
      • Berghella V.
      • Wenstrom K.D.
      • Mercer B.M.
      • Saade G.R.
      Preventing the first cesarean delivery: summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists workshop.
      American College of Obstetrics and Gynecology; Society for Maternal-Fetal Medicine
      Safe prevention of the primary cesarean delivery. Obstetric care consensus no. 1.
      This is an opportunity to lower the rate in view of the emerging data suggesting that the majority of the increase in the rate is attributed to relatively subjective clinical risk factors such as nonreassuring fetal status and labor arrest disorders than to more objective risk factors such as maternal and fetal medical risk factors.
      • Barber E.L.
      • Lundsberg L.S.
      • Belanger K.
      • Pettker C.M.
      • Funai E.F.
      • Illuzi J.L.
      Indications contributing to the increasing cesarean delivery rate.
      Although changes in the prevalence of maternal and fetal medical risk factors are not the dominant driver of the increase in the cesarean delivery trend, they are important contributors to the rate and must be carefully evaluated in the definition of a low-risk cesarean delivery rate. A low-risk cesarean delivery rate definition that has enhanced face validity, is more comprehensive, and is accepted by clinicians could help move the momentum forward toward achieving the Healthy People 2020 goals of reducing cesarean births among low-risk (full-term, singleton, and vertex presentation) women.

      US Department of Health and Human Services. Office of Disease Prevention and Health Promotion. Healthy people 2020. Washington (DC). Available at: http://www.healthypeople.gov/2020/topics-objectives/topic/maternal-infant-and-child-health/objectives. Accessed May 15, 2015.

      A more clinically robust definition of low risk is also important when evaluating hospital-level variation and obtaining hospital buy-in of measurement. Low-frequency, high-risk diagnoses that are maintained in the definition could overstate the cesarean delivery rate and skew hospital comparison in the same geographic area. This ultimately undermines physician buy-in. At worst, it could result in perceived disincentives for clinicians to care for women with these complications if the quality measures for the care these patients receive does not appropriately account for their disproportionate risks.
      We have created a definition to identify women at low risk for cesarean delivery. The definition is claims based, is relatively easy to program, and does not require additional hospital resources for data abstraction. Not surprisingly, we observed that this refined definition applied to a nationally representative sample of US hospitals providing obstetric delivery services resulted in lower risk-adjusted cesarean delivery rates than the JC or AHRQ measure for all hospitals strata (hospital size, geography, teaching status, and payer type).
      Importantly, a single, consistent accepted measure is necessary to track national progress in safely lowering the cesarean delivery rate. The SMFM measure achieves all measurement goals while also addressing previous clinician concerns. Engagement of frontline clinicians is essential in working toward achieving Healthy People 2020.

      Limitations

      A number of limitations of our analysis merit discussion. The proposed code set to define low risk for cesarean delivery, while comprehensive, does not delineate every clinical scenario. It does not, for example, consider the additive effect of multiple risk factors that individually may not constitute high risk for cesarean delivery but do when combined. Additionally, the classification of risk factors changes as literature and practice guidelines evolve. Thus, our proposed code set represents a starting point to get to a clinically valid definition of low risk. It should be evaluated and updated on a regular basis. To ensure sufficient volume per hospital for comparison, we excluded hospitals with <100 deliveries in 2011, and thus our findings may not generalize to hospitals with small-volume obstetrical units. While there are no nationally representative data sets in the United States that contain a greater level of detail on childbirth-related health care services than the data we used in this study, it does not include clinician-level information. Thus cesarean delivery rate differences due to the specialty training or discipline of the attending clinicians within a hospital (eg, midwifery, family medicine, maternal-fetal medicine) cannot be evaluated. Additionally, our analysis of the risk-adjusted cesarean delivery rate is based on claims data alone and does not allow a review of the clinical reasons for cesarean delivery that chart review would allow. Potential bias may result from clinical differences not identifiable in administrative data or misclassification due to inaccurate recording of complications or comorbidities using claims-based data only.
      • Berthelsen C.L.
      Evaluation of coding data quality of the HCUP Nationwide Inpatient Sample.
      • Robson M.
      Classification of cesarean sections.
      It is not expected that this type of bias would affect any 1 definition differently. And while this type of bias could be minimized with supplemental risk adjustment using linked birth or hospital records, the simplicity of using administrative data alone and a code-based measure cannot be overstated. The transition from ICD-9 to International Statistical Classification of Diseases, 10th Revision coding will result in the incorporation of greater specificity in the description of clinical services, including obstetrical risk factor description. Efforts to map ICD-9 to International Statistical Classification of Diseases, 10th Revision coding are in development and can be used to update this low-risk cesarean rate definition to the new coding set when available. Finally, we did not correlate cesarean delivery rates with neonatal outcomes as this was beyond the scope of this evaluation. Despite these limitations, we believe that we have provided a practical approach to identifying low-risk women with regard to cesarean delivery. No measure is perfect. Since the ultimate goal is to track changes over time and in response to various interventions, any of the 3 definitions can be used, as long as it is used consistently to track cesarean rates over time within a particular health care system.

      Conclusion and future use of the SMFM definition

      We have created a low-risk cesarean delivery rate definition using a refined code set of ICD-9 claims-based data. This refined definition sought to maximize face validity by excluding from the definition of low risk those diagnosis codes that are absolute or relative contraindications to vaginal birth but including in the definition other factors that are known to be discretionary risk factors for cesarean delivery and drivers of the high US cesarean delivery rate. When this refined definition is applied to a nationally representative sample of US hospitals providing obstetric delivery services, it resulted in lower risk-adjusted cesarean delivery rates than the JC or AHRQ measure for all hospitals strata (hospital size, geography, teaching status, and payer type). The greater precision in the definition of low risk increases the clinical accuracy of the definition. Thus, it allows for the identification of the causes of modifiable variation in cesarean delivery rates among hospitals to effectively and safely lower them. The ease of use of the definition and the enhanced face validity of the definition have the potential to empower hospitals and health care providers to keep up the momentum to effectively and safely lower cesarean delivery rates among low-risk women. This enhanced definition should be adopted into ongoing refinement of existing measures with a goal of establishing a single, universally recognized measure.

      References

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