Risk adjustment in maternity care: the use of indirect standardization

Abstract

PurposeAnnual US national rates of family physicians providing maternity care are decreasing and rates of cesarean delivery are increasing. Family physicians tend to have lower cesarean delivery rates than obstetrician specialists, but this association is usually explained by an assumed lower pre-delivery risk for cesarean delivery. This study was developed to compare the estimated risk of cesarean delivery in patients of the two specialties.MethodsA retrospective cohort study within an urban teaching hospital compared 100 family- physician treated subjects to 300 subjects treated by obstetrician-specialists. Risk factors for cesarean delivery were identified, and an indirect standardization procedure was used to compare the pre-38 week of gestation risk of cesarean delivery in the two groups.ResultsThe patients treated by family physicians had a projected pre-38 week of gestation risk of cesarean delivery (17.4%) that was similar to the actual rate of cesarean delivery in the obstetrician-specialist group (16.7%). The Standardized Cesarean Delivery Ratio was 1.04.ConclusionLower cesarean delivery rates provided by family physicians may not be simply due to case-mix issues. Additional studies comparing the pre-delivery estimation of cesarean delivery risk would be helpful in measuring the relative levels of obstetric risk of patients treated by different maternity-care provider types.

Cesarean delivery rates among family physicians versus obstetricians: a population-based cohort study using instrumental variable methods

“…We feel that instrumental variable methods are the most appropriate to answer our research question because they address criticisms from previous work: that unmeasured factors contribute to observed differences in cesarean delivery rates between family physicians and obstetricians. [8][9][10][11] However, because of the novelty and magnitude of our findings and because of the methodological limitations outlined below, our findings require confirmation before a clinical or policy response should be considered.…”

“…However, the risk factors outlined in Table 1 are traditional obstetrical comorbidities. Family physicians may care for populations that are higher risk owing to sociocultural and other reasons, 7,11 and these variables are not captured in the administrative data used for this study (Appendix 1). If this is the case, unobserved factors that affect treatment decisions would be unevenly distributed between the experimental groups in our study, which would violate the assumptions required for instrumental variable analyses (i.e., instrumental-variable-adjusted analyses may be biased).…”

Neonatal Outcomes of 26,331 Infants Delivered by Obstetrics Fellowship Trained Family Physicians and OB/Gyns

“…The incidence of 2 American Board of Family Medicine. 3 American Board of Obstetrics and Gynecology. 4 Three family physicians completed 1 year obstetrics fellowships.…”

“…for years [1][2][3][4]. There is little difference in infant morbidity when family physicians were compared to obstetricians [5].…”