Background
Reducing cesarean deliveries is a major public health goal. The low rate of vaginal birth after cesarean has been attributed largely to a decrease in the likelihood of choosing a trial of labor after cesarean, despite evidence suggesting a majority of women with 1 prior low transverse cesarean are trial of labor after cesarean candidates. Although a number of reasons for this decrease have been explored, it remains unclear how systems issues such as physician call schedules influence delivery approach and mode in this context.
Objective
The objective of the study was to investigate the relationship between obstetricians’ call schedule and obstetric outcomes among women eligible for a trial of labor after cesarean.
Study Design
This is a retrospective cohort study of the likelihood of attempting a trial of labor after cesarean and achieving vaginal birth after cesarean among women with 1 prior low transverse cesarean delivery and a term, cephalic singleton gestation based on the delivering provider’s call schedule. Attending obstetrician call schedules were classified as traditional or night float call. Night float call was defined as a schedule in which the provider had clinical responsibilities only for a day or night shift, without other clinical responsibilities before or after the period of responsibility for laboring patients. Call schedules are determined by individual provider groups. Bivariable analyses and random-effects logistic regression were used to examine the relationship between obstetricians’ call schedule and the frequency of trial of labor after cesarean. Secondary outcomes including frequency of vaginal birth after cesarean and maternal and neonatal outcomes also were assessed.
Results
Of 1502 eligible patients, 556 (37%) were delivered by physicians in a night float call system. A total of 22.6% underwent a trial of labor after cesarean and 12.8% achieved vaginal birth after cesarean; the vaginal birth after cesarean rate for women attempting a trial of labor after cesarean was 56.5%. Women were more likely to undergo a trial of labor after cesarean (33.1% vs 16.5%, P < .001) and achieve vaginal birth after cesarean (18.7% vs 9.3%, P < .001) when cared for by physicians with a night float call schedule. Regression analyses demonstrated physicians with a night float call schedule remained significantly more likely to have patients undergo trial of labor after cesarean (adjusted odds ratio, 2.64, 95% confidence interval, 1.65–4.25) and experience vaginal birth after cesarean (adjusted odds ratio, 2.17, 95% confidence interval, 1.36–3.45) after adjusting for potential confounders. However, the likelihood of achieving vaginal birth after cesarean if a trial of labor after cesarean was attempted was not different based on provider call type (adjusted odds ratio, 0.96, 95% confidence interval, 0.57–1.62). Although women delivered by providers with a night float schedule were more likely to experience uterine rupture (1.8% vs 0.6%, P = .03), chorioamnionitis (4.3% vs 1.7%, P = .002), postpartum hemorrhage (7.6% vs 4.8%, P = .03), and neonates admitted to the neonatal intensive care unit (6.8% vs 3.9%, P = .01), these associations did not persist when the population was limited to women attempting trial of labor after cesarean.
Conclusion
Although physicians working on a night float call system were significantly more likely to have patients with a prior cesarean undergo trial of labor after cesarean and achieve vaginal birth after cesarean, their patients also were more likely to experience maternal and neonatal morbidity. However, these differences did not persist when limiting analyses to women attempting a trial of labor after cesarean. Using a night float call schedule may be an effective measure to promote a trial of labor after cesarean and vaginal birth after cesarean.
The rising cesarean delivery rate in the United States is a substantial public health and clinical concern. Approximately 90% of low-risk women with a prior cesarean delivery undergo repeat cesarean delivery, and data from 2003 to 2009 suggest the increase in repeat cesarean deliveries has contributed to half of the increase in the cesarean rate.
Reducing both primary and repeat cesarean deliveries is a goal of numerous professional organizations and the US Department of Health and Human Services. With regard to repeat cesarean deliveries, the decrease in the vaginal birth after cesarean rate has been attributed largely to a decrease in the likelihood of choosing a trial of labor after cesarean, despite evidence suggesting a majority of women with 1 prior low transverse cesarean are trial of labor after cesarean candidates. Although many factors contribute to delivery decisions in the setting of a prior cesarean delivery, little work has addressed how systems issues such as physician call schedules influence delivery approach and mode.
The American College of Obstetricians and Gynecologists notes that after appropriate counseling, “the ultimate decision to undergo trial of labor after cesarean or a repeat cesarean delivery should be made by the patient in consultation with her health care provider.” Yet a growing body of evidence suggests providers influence patient decisions via directive counseling as well as other more indirect provider attributes.
One potential provider factor that may influence delivery approach is the type of call schedule, or the manner in which a physician’s group handles nighttime hospital responsibilities. Prior work by Barber et al found that the transition from a traditional call schedule to a night float system was associated with changes in practice patterns at the time of delivery. Specifically, patients were less likely to undergo induction of labor or receive an episiotomy when cared for by a physician working in a night float system; in addition, major perineal lacerations and umbilical artery pH <7.10 were less frequent with a night float system. These data suggest physician factors such as call schedule may be associated with intrapartum decision making and care.
However, these relationships have not been studied for women who have 1 prior cesarean delivery and are eligible for trial of labor after cesarean. Understanding these relationships may identify an additional important avenue by which the rising cesarean delivery rate may be addressed from a systems perspective.
It is plausible that physicians who practice in a night float system, in which nighttime providers caring for laboring patients are not responsible for postcall clinical activities and daytime providers are not responsible for clinical care at night after a full clinical day, may be more likely to offer trial of labor after cesarean to eligible patients because of less concern for achieving daytime deliveries to ease nighttime or postcall clinical responsibilities.
This greater likelihood of offering a trial of labor after cesarean may then be associated with an increased rate of vaginal birth after cesarean. Thus, we designed this study to assess the association between physician type of call schedule and the likelihood of trial of labor after cesarean and vaginal birth after cesarean in a population of women eligible for trial of labor after cesarean.
Materials and Methods
This is a retrospective cohort study of women delivering at a single institution who were eligible to undergo a trial of labor after cesarean. Patients eligible for study inclusion were primiparas aged 18 years or older with 1 prior low transverse cesarean delivery and a term, cephalic singleton gestation. All deliveries meeting criteria from January 2008 to June 2013 were reviewed to provide a final population for analysis that would allow for adequate power.
The population was limited to women with 1 prior cesarean delivery and no prior vaginal delivery to restrict the cohort to a low-risk trial of labor after cesarean candidates whose delivery approach counseling would not have been influenced by prior vaginal birth(s) or multiple prior cesarean deliveries. Women with fetuses who had major anomalies, who had a fetal demise, or who were otherwise ineligible for vaginal birth (placenta previa, prior classical cesarean delivery, prior cavity-entering myomectomy) were excluded. Women were not excluded for medical comorbidities unless those comorbidities were contraindications to labor.
Data were abstracted from the electronic medical record. Institutional review board approval from Northwestern University was obtained prior to the initiation of the study.
Attending physicians caring for each patient were categorized as either traditional call (n = 58) or night float (n = 36) call; these 94 obstetricians comprised 82% of the obstetricians delivering at this institution over the study period. Night float providers were those who practiced in a group where the on-call night obstetrician provided hospital care for several nights sequentially without daytime office or other clinical responsibilities.
Groups had different numbers of sequential nights in a night float system, but all providers categorized as night float were those whose only clinical responsibility was for hospitalized patients in either a day or night shift; shifts were followed by time for sleep prior to a subsequent shift. All other provider call types were classified as traditional call, in which physicians performed daytime clinical responsibilities followed by nighttime call (either home or in the hospital), with possible subsequent partial or full-day clinical responsibilities the next day. All providers in this study practiced in a group setting, with all physicians in a group adhering to the same type of call schedule.
Call schedule types were at the discretion of each group. All deliveries at this institution are managed and attended by a member of the patient’s provider group, with an in-house obstetrician available for emergency backup. Resident physicians are involved in the care of all patients with a prior cesarean delivery, and resident physicians function on a night float call system; thus, the analysis was assessed on the basis of the call schedule of the delivering attending physician’s group. All final decisions about undergoing a trial of labor after cesarean or intrapartum care are made by attending physicians.
Sample size was determined based on the number of patients needed to demonstrate a difference in the rate of a trial of labor after cesarean between patients delivered by providers with night float vs traditional call. Prior work has suggested an institutional trial of labor after cesarean rate of approximately 22%, and work by Barber et al suggested a 40% relative difference in induction of labor rates based on call type. Assuming a 1:2 patient ratio for night float to traditional call based on knowledge of practice patterns at this institution, 1053 patients are required for 90% power, with an alpha of 0.05 to detect a similar relative difference in trial of labor after cesarean rate.
The primary outcome was frequency of trial of labor after cesarean. Secondary outcomes included frequency of vaginal birth after cesarean (ie, both overall vaginal birth after cesarean rate and vaginal birth after cesarean rate if the trial of labor after cesarean was attempted) and maternal and neonatal adverse outcomes. Maternal secondary outcomes included uterine rupture (defined as uterine rupture with clinical consequence for the mother or fetus and not including an incidentally noted uterine window or scar dehiscence), maternal chorioamnionitis (defined as a temperature >100.3°F without an identified etiology other than intrauterine infection), postpartum hemorrhage (defined as estimated blood loss >500 mL for a vaginal delivery or >1000 mL for a cesarean delivery), major perineal lacerations (defined as a third- or fourth-degree laceration), episiotomy, and maternal intensive care unit admission. Neonatal outcomes included 5-minute Apgar score ≤4, umbilical cord artery pH <7.0, sepsis, seizures, hypoxic ischemic encephalopathy, and admission to the neonatal intensive care unit.
We compared patient characteristics stratified by their physician’s call type using χ 2 , t-tests and Mann-Whitney U tests. Bivariable analyses of the primary and secondary outcomes were then assessed using χ 2 tests or Fisher’s exact test. Random-effects multivariable logistic regression models were utilized to examine relationships between physician call schedule and the odds of primary and secondary outcomes.
The regression analysis adjusted for potential confounders, including patient characteristics identified to be significantly associated in a bivariable analysis ( P < .1) with provider call type, and delivering physicians; the latter were entered into the regression as random-effects terms to account for the effect of nonindependence because of clustering by physician and to account for differences in physicians.
Secondary outcomes were not adjusted for the mode of delivery because the delivery route is on the causal pathway for many outcomes; however, where relevant, the population was limited to those choosing a trial of labor after cesarean because certain outcomes are not possible if a trial of labor after cesarean is not undertaken (episiotomy, major perineal laceration, and shoulder dystocia).
A further analysis was performed in which the odds of vaginal birth after cesarean and the odds of adverse maternal and neonatal outcomes were analyzed in a sample restricted to those undergoing a trial of labor after cesarean. Statistical analyses were undertaken using Stata version 13 (Stata Corp, College Station, TX). All analyses were 2 tailed and P < .05 was used to define statistical significance.
Results
In this cohort, 1502 women met criteria for inclusion. Of these, 556 (37%) were delivered by physicians who use a night float call system. The majority of patients were privately insured, non-Hispanic white race/ethnicity, and older than age 30 years ( Table 1 ). Patients did not differ on most characteristics based on their physicians’ call schedule, including with respect to maternal age, race/ethnicity, insurance status, or neonatal birthweight. Women delivered by night float physicians had a statistically, although not clinically meaningfully, later mean gestational age at delivery (39.2 vs 39.1 weeks, P < .001) than women delivered by physicians with a night float system. Patients delivered by night float call physicians were more likely to deliver between 7:00 pm and 7:00 am (40.0 vs 15.8%, P < .001).
| Characteristics | Traditional call (n = 946) | Night float (n = 556) | P value |
|---|---|---|---|
| Age, y | 33.8 ± 4.5 | 34.1 ± 4.7 | .35 |
| Body mass index, kg/m 2 | 30.8 ± 6.0 | 30.3 ± 5.3 | .09 |
| Ethnicity | .47 | ||
| White | 648 (68.5%) | 396 (71.2%) | |
| African American | 95 (10.0%) | 55 (9.9%) | |
| Hispanic | 132 (14.0%) | 62 (11.2%) | |
| Asian | 71 (7.5%) | 43 (7.7%) | |
| Insurance | .97 | ||
| Private | 875 (92.5%) | 514 (92.5%) | |
| Medicaid | 71 (7.5%) | 42 (7.6%) | |
| Gestational age, wks | 39.1 ± 0.7 | 39.2 ± 0.8 | < .001 |
| Birthweight, g | 3518 ± 458 | 3547 ± 472 | .23 |
| Delivery between 7:00 pm and 7:00 am | 184 (15.8%) | 136 (40.0%) | < .001 |
In the study population, 340 women (22.6%) underwent a trial of labor after cesarean. In total, 1310 women (87.2%) experienced cesarean delivery, and 192 (12.8%) experienced vaginal birth after cesarean. Of those attempting a trial of labor after cesarean, the vaginal birth after cesarean rate was 56.5%. Differences in delivery approach and mode based on provider call type are demonstrated in Table 2 . Women who were delivered by a night float physician were more likely to undergo a trial of labor after cesarean than women who were delivered by a traditional call physician (33.1% vs 16.5%, P < .001).
| Variables | Bivariable analysis | Multivariable analysis a | |||
|---|---|---|---|---|---|
| Traditional call (n = 946) | Night float (n = 556) | P value | Unadjusted OR (95% CI) | Adjusted OR (95% CI) | |
| TOLAC | 156 (16.5%) | 184 (33.1%) | < .001 | 2.50 (1.96–3.20) | 2.64 (1.65–4.25) |
| VBAC | 88 (9.3%) | 104 (18.7%) | < .001 | 2.24 (1.65–3.05) | 2.17 (1.36–3.45) |
| VBAC if TOLAC attempted | 88 (56.4%) | 104 (56.5%) | .98 | 1.00 (0.65–1.55) | 0.96 (0.57–1.62) |
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