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Nulliparous term singleton vertex cesarean delivery rates: institutional and individual level predictors

OBJECTIVE: This study was undertaken to determine individual and institutional level variables predictive of variations in nulliparous term singleton vertex cesarean delivery rates.

STUDY DESIGN: A retrospective cohort study of 28,863 nulliparous term singleton vertex births at 40 Arizona hospitals.

RESULTS: The average nulliparous term singleton vertex cesarean delivery rate was 22.0%, the lowest hospital rate was 10.3%, high, 34.2%. The following individual-level variables increased the nulliparous term singleton vertex cesarean delivery rate in a multivariable model: increased mother’s age, African American race, increased birth weight, labor induction, and the presence of medical conditions such as diabetes and hypertension. Of the institutional variables, after adjustment, the highest level of nursery or a higher percentage of government-paid births was associated with lower risks, whereas delivery at a hospital with the lowest level of care or with an obstetric and gynecology residency was associated with an increased risk of cesarean delivery.

CONCLUSION: Substantial variations in nulliparous term singleton vertex cesarean delivery rates were seen in this comparative analysis of 40 hospitals.

Summary of the Study

Studies of cesarean deliveries present a rich picture of variations in cesarean delivery rates. These have examined overall cesarean delivery rates and primary cesarean delivery rates. These studies have shown variations by both clinical and nonclinical factors, including the presence or absence of conditions such as diabetes, preeclampsia, advanced maternal age, and various institutional factors.

However, these studies have limitations because, for example, the overall cesarean delivery rate is heavily influenced by the vaginal birth after cesarean rate, and the primary cesarean delivery rate does not necessarily adjust for medical risk factors. As a result, models have been created to adjust for risks through regression models or standardization.

However, these have not been widely adopted as quality measures, because of their complexity, the lack of agreement over which factors should be adjusted, and questionable validity of various risk factors when derived from administrative data.

Another method, risk stratification, attempts to create homogenous groups from which to make comparisons. Once such method compares cesarean rates among the “standardized nulliparous patient” introduced in Britain. This rate was broadened and adopted as the nulliparous, term, singleton, vertex (NTSV) cesarean delivery (CD) rate by the US Department of Health and Human Services in their Healthy People 2010 goals and the American College of Obstetrics and Gynecology (ACOG) as a possible quality measure.

Despite its adoption, studies examining this measure have been limited. Main et al9 published a study that revealed substantial variations between hospitals that were predicted by higher rates of induced labor and earlier admissions in labor. Variations, based on maternal age were also found, and the authors suggested using direct standardization by age to compare hospitals. The study by Main et al was based on 20 hospitals belonging to a single network. Other studies that used measures similar to NTSV CD rates have also shown variations in the rate.

In our study, we explored the NTSV concept by studying variations among hospitals in the State of Arizona, based on factors collected on birth certificates and easily available institutional data, to further understand this possibly quality measure. We designed a retrospective cohort study to examine individual-level risk factors for variations in NTSV rates. We also examined institutional-level risk factors for NTSV CD. Finally, these factors were combined in a multivariable model controlling for clinical and nonclinical risk factors, to study variations among hospitals in NTSV CD rates.

Keywords: cesarean delivery, nulliparous woman, ovarian cancer, parous women, risk factor, multiparous women, breast cancer risk, vaginal delivery, eclampsia, pregnancy, cesarean section, preterm birth, cervical dilation, nulliparous patients, pregnant woman

Her service commitments include multiple leadership positions with the American College of Obstetricians and Gynecologists and as an oral examiner for the American Board of Obstetricians and Gynecologists.

Dr. Manriquez continues clinical practice, focusing on substance use disorders in pregnancy and parenting women. Her research and advocacy focus is aimed at investigating innovations in prenatal care models addressing maternal morbidity and mortality, preterm delivery rate and substance use disorders in pregnancy.

Outside of her roles within medicine, Dr. Manriquez said family is most important to her. She is married to Moses Sanchez and has three children. “I like to say I birthed my best friend,” she said. Her daughter, Bernadine Sadauskas, is the department administrator for Frederic Zenhausern, PhD, MBA, and the Center for Applied NanoBioscience and Medicine, which Dr. Zenhausern directs.

“We live next door to each other,” Dr. Manriquez said of her daughter. “We opened up the backyard between our houses. My three grandchildren live next door. We are well-rooted in our faith. Outside of that, I love to travel, and I like to write. I enjoy what I do in women’s health and serve my patients at MIHS.”

Dr. Manriquez is able to prescribe buprenorphine, a partial opioid agonist that is used to treat opioid addiction and manages patients who need this care in pregnancy. She plans to sit for boards in Addiction Medicine this fall. She developed and is co-program director for Reentry into the Obstetrics and Gynecology Clinical Practice at Maricopa Integrated Health System.

She has been active in numerous leadership roles within and outside of the College, including the American College of Obstetricians and Gynecologists.

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