Background
Laborist practice models are associated with lower rates of cesarean delivery than individual private practice models in several studies; however, this effect is not uniform. Further exploration of laborist models may help us better understand the observed decrease in rates of cesarean delivery in some hospitals that implement a laborist model.
Objective
Our objective was to evaluate the degree of variation in rates of primary cesarean delivery by individual laborists within a single institution that uses a laborist model. In addition, we sought to evaluate whether differences in rates of cesarean delivery resulted in different maternal or short-term neonatal outcomes.
Study Design
At this teaching institution, one laborist (either a generalist or maternal−fetal medicine attending physician) is directly responsible for labor and delivery management during each shift. No patients are followed in a private practice model nor are physicians incentivized to perform deliveries. We retrospectively identified all laborists who delivered nulliparous, term women with cephalic singletons at this institution from 2007 to 2014. Overall and individual primary cesarean delivery rates were reported as percentages with exact Pearson 95% confidence intervals. Laborists were grouped by tertile as having low, medium, or high rates of cesarean delivery. Characteristics of the women delivered, indications for cesarean delivery, and short-term neonatal outcomes were compared between these groups. A binomial regression model of cesarean delivery was estimated, where the relative rates of each laborist compared with the lowest-unadjusted laborist rate were calculated; a second model was estimated to adjust for patient-level maternal characteristics.
Results
Twenty laborists delivered 2224 nulliparous, term women with cephalic singletons. The overall cesarean delivery rate was 24.1% (95% confidence interval 21.4−26.8). In an unadjusted binomial model, the overall effect of individual laborist was significant ( P < .001), and a 2.9-fold (1.5−5.4, P = .001) variation between the cesarean delivery rates of the greatest (35.9%) and lowest (12.5%) physicians was observed. When adjusted for hypertensive disease, gestational age at delivery, race, and maternal age, the physician effect remained overall significant ( P = .0265) with the difference between physicians expanding to 3.58 (1.72−7.47, P <. 001). Between groups of laborists with low, medium, and high rates of cesarean delivery, patient demographics and clinical characteristics of the population managed were clinically similar and not different statistically. The primary indication for cesarean delivery did not differ between groups. Similarly there were no differences in short-term neonatal outcomes, including Apgar scores, arterial cord blood pH, or the incidence of neonatal encephalopathy.
Conclusion
The 3-fold variation in cesarean delivery rates between laborists at the same institution without observed differences in patient characteristics or short-term neonatal outcomes draws attention to the impact of individual physician decision-making on cesarean delivery rates even within a laborist care model. Further exploration of the role of individual physician decision-making on cesarean rates may help to better elucidate the effect of the laborist model.
With the ongoing increase in the rate of cesarean delivery in the United States, many organizations and investigators are working to develop guidelines and evidence-based practice to help stabilize and ultimately decrease the number of cesarean deliveries. Prevention of the primary cesarean delivery has gained traction as the most obvious point of intervention to prevent future cesarean deliveries and future morbidity associated with cesarean deliveries. The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine developed a consensus statement with guidelines to help prevent cesarean deliveries that included suggestions for tolerated length of second stage, use of operative vaginal delivery in appropriate candidates, and length of augmentation before performing a cesarean delivery for arrest disorders.
Other investigators have evaluated different care models, and a “laborist” (or obstetric hospitalist) model has been found to decrease the rate of cesarean delivery compared with traditional models of obstetrical care. An ACOG Committee Opinion defines a laborist as an obstetrician−gynecologist who is used by the hospital to manage laboring patients and attend to obstetric emergencies. Given this definition, this decrease in cesarean delivery is plausible with the increased availability of the laborist, focused expertise in labor management, and potentially a greater objectivity in assessing the clinical scenario when not managing a private patient. There is a large study, however, in which the same decrease in cesarean delivery was not observed with a laborist model. In addition, a survey-based study noted an association between laborists and an increased likelihood to perform cesarean delivery when provided with clinical vignettes.
It may be that the observed decrease in cesarean delivery with the laborist model in some studies is a reflection of not just the laborist care model but also the individual laborists. Previous training, experience, comfort with specific skills, and cognitive traits likely all influence care of individual physicians in a given clinical scenario. These differences between individuals may result in differing rates of primary cesarean delivery even within the same clinical setting.
Our objective was to evaluate the degree of variation in rates of primary cesarean delivery by individual laborists within a single institution that uses a laborist model to better understand the observed decrease in cesarean delivery observed in some studies.
Materials and Methods
This was a retrospective cohort study of all women who delivered at a single center from December 2007 through May 2014. Women who delivered during this time period were identified from the electronic medical record charting system used on Labor and Delivery for nursing charting (OBTraceVue). Nulliparous women with a term, cephalic singleton pregnancy and no contraindication to vaginal delivery (previa, active herpes infection, human immunodeficiency virus with a viral load >1000 copies/mL, previous uterine surgery, malpresentation) were included. All women who were managed primarily by our midwifery service were excluded from this study. This study was approved by the Colorado Multiple Institutional Review Board.
Data for the cohort were collected from 3 sources: OBTraceVue, individual patient medical records, and the Denver Health Data Warehouse. The Denver Health Data Warehouse is an institution-wide administrative database of all admissions and outpatient visits within the Denver Health system. The Data Warehouse contains both demographic information and clinical data including billing codes and all laboratory results for each admission. The Data Warehouse was used to extract demographic characteristics (payor source, race, and ethnicity), cord blood gases, and billing codes for hypertensive disease (preeclampsia, chronic hypertension and gestational hypertension), preexisting diabetes, and gestational diabetes.
Clinical obstetric data were extracted primarily from nursing charting in OBTraceVue with supplemental detailed chart abstraction by 2 obstetricians (T.D.M. and S.A.B.G.) for intrapartum course and indication for primary cesarean delivery. When the primary indication for cesarean delivery was not clear in the operative report, we developed an algorithm for assigning the primary and secondary indication for cesarean delivery. In cases in which it was unclear whether the primary indication was an arrest disorder or nonreassuring fetal status, the arrest disorder was selected as the primary indication and nonreassuring fetal status was selected as the secondary indication. Analyses were then performed to assess the primary indication, secondary indication, and nonreassuring fetal status as either the primary or secondary indication to evaluate whether there were differences between physician group by indication for cesarean delivery.
All deliveries in the cohort were assigned to the laborist (attending physician) who staffed the delivery. All laborists in the practice were included in the analysis regardless of the number of deliveries managed. Laborists at this institution are assigned to shifts on Labor and Delivery months in advance to allow for in-house laborist coverage at all times. No patients in the practice are followed in a private practice model. Resident physicians are involved in the care of all women on Labor and Delivery. The laborist on-call is responsible for the intrapartum management of all women in labor and any obstetric emergencies. We do not perform elective inductions at our institution, and women are not scheduled for inductions or scheduled procedures on a day when a particular laborist is staffing the floor. This protocol differs from a university coverage model in that the laborists are assigned only to Labor and Delivery. There are no competing outpatient responsibilities, and none of the women seen in our practice identify a particular attending as their private care provider. Laborist coverage assignments are based on the clinical time of individual physicians and are distributed as a mix of daytime and night and weekend coverage. Within our laborist model, education of residents and backup of midwives and family practice physicians also is provided, consistent with the definition of a laborist by ACOG.
The rate of primary cesarean delivery for each attending laborist was calculated by dividing the number of cesarean deliveries for each laborist by the total number of deliveries staffed by that individual laborist over the study time period. Individual laborist cesarean delivery rates are reported with exact Pearson 95% confidence intervals.
Individual laborists were then divided into 3 groups by tertile of low, medium, and high rates of cesarean delivery. To determine whether significant differences existed in the population of women managed by the 3 groups of laborists, the basic demographics and clinical characteristics of the women they delivered were compared. Short-term neonatal outcome data were compared across provider tertile to determine whether different rates of cesarean delivery were associated with differences in outcomes. Comparisons between groups were made with the χ 2 for categorical and analysis of variance for continuous measures.
A binomial regression model of cesarean delivery was estimated with SAS Glimmix (SAS, Cary, NC), where the relative rates of each laborist compared with the lowest-unadjusted laborist rate were calculated; a second model was estimated to adjust for patient-level maternal characteristics (hypertensive disease, race, maternal age, gestational age at delivery) associated with cesarean delivery to further assess the effect of individual laborists on cesarean delivery.
Individual physician characteristics (male vs female, years in practice, maternal−fetal medicine vs generalist, and delivery volume) also were evaluated to determine whether there was an association between these factors and rates of cesarean delivery. Comparisons were made by physician tertile and modeled by the use of a general linear mixed effects model to adjust for within-physician correlation.
P < .05 was considered statistically significant. All analyses were completed in SAS 9.4 (SAS), with graphics created using GraphPad Prism v6.03 (GraphPad Software, Inc, La Jolla, CA). Data from clinical chart abstraction were managed before analysis with use of the secure, web-based application Research Electronic Data Capture (REDcap) hosted at University of Colorado.
Results
The total number of women who delivered at our institution during the 7-year study time period was 22,006. There were 4139 term, nulliparous deliveries in cephalic presentation with an overall rate of cesarean delivery of 18% among these women. After excluding deliveries managed by our midwifery service (n = 1658) and deliveries without a documented laborist as the attending (n = 257), the overall rate of cesarean delivery of our analyzed cohort was 24.1% (95% confidence interval 22.4−26.0).
Twenty laborists delivered the 2224 nulliparous, term women with cephalic singletons included in our analysis. The number of deliveries per laborist ranged from 11 to 390 (interquartile range, 52−139).
In the tertile with the lowest cesarean delivery rate, 7 laborists had a total of 559 deliveries between them; with individual rates of cesarean delivery between 12.5 and 22.1%. The 6 laborists in the tertile with the medium cesarean delivery rate had 951 deliveries between them, with rates of cesarean ranging from 23.1 to 24.6. In the tertile with the greatest rate of cesarean delivery, 7 laborists had 714 deliveries between them, with rates of cesarean delivery ranging from 25.0 to 35.9%. We assessed the internal validity of grouping the laborists into tertiles. In accordance with the defined tertiles, there were statistically significant differences between groups for cesarean delivery rate (19% low, 24% medium, 29% high, P < .001).
In an unadjusted binomial model, the overall effect of individual laborist was significant ( P < .001), and a 2.9-fold (1.5−5.4, P = .001) variation between the cesarean delivery rates of the greatest (35.9%) and lowest (12.5%) physicians was observed ( Figure 1 ). When adjusted for hypertensive disease, gestational age at delivery (<39, 39, 40, 41+ weeks), race (black, Hispanic, white, other), maternal age (<18, 19-<25, 25-<30, 30-<35, and 35+ years), and the hypertension and gestational age interaction, the physician effect remained overall significant ( P = .0265) with the difference between physicians expanding to 3.58 (1.72−7.47, P < .001). Between groups of laborists with low, medium, and high rates of cesarean delivery, there were no significant differences in patient demographics or clinical characteristics of the population managed ( Table 1 ).
| Characteristics | Low cesarean rate (n = 559) | Medium cesarean rate (n = 951) | High cesarean rate (n = 714) | P value |
|---|---|---|---|---|
| Race | .77 | |||
| White | 88 (15.94) | 149 (16.00) | 121 (17.24) | |
| Hispanic | 353 (63.95) | 625 (67.13) | 452 (64.39) | |
| Black | 77 (13.95) | 110 (11.82) | 91 (12.96) | |
| Other | 34 (6.16) | 47 (5.05) | 38 (5.41) | |
| Maternal age, geomean (95% CI) | 22.6 (22.2−23.0) | 22.3 (22.0−22.7) | 22.6 (22.2−23.0) | .53 |
| Induction | 134 (25.2) | 215 (23.5) | 180 (25.9) | .50 |
| Cervical dilation at admission, mean (SE) | 3.56 (0.10) | 3.57 (0.09) | 3.41 (0.10) | .45 |
| Gestational age at delivery, mean (SE) | 39.7 (0.05) | 39.7 (0.04) | 39.6 (0.05) | .89 |
| Hypertensive disease a | 123 (22.0) | 208 (21.9) | 179 (25.1) | .26 |
| Gestational or preexisting diabetes | 51 (9.1) | 73 (7.7) | 45 (6.3) | .17 |
a Hypertensive disease includes women with chronic hypertension, gestational hypertension, or preeclampsia.
Among only the women who had a cesarean delivery, the percentage of women with an arrest disorder as the primary indication for cesarean delivery did not differ between groups. Similarly, the percentage of women with nonreassuring fetal status as the primary indication for cesarean delivery did not differ between groups ( Table 2 ). However, as expected, the percentage of all women in the cohort (cesarean delivery/ total population managed) who underwent cesarean delivery increased across tertiles for both indications (14.7%, 16.0%, 20.0% for arrest disorders and 4.5%, 7.0%, 8.5% for nonreassuring fetal status). Nonreassuring fetal status was the primary or secondary indication for cesarean delivery in 5.9% vs 7.9% vs 10.2% of women managed. In short, laborists in the highest tertile did more cesarean deliveries for both of these indications.
