Background
Because nearly one-third of births in the United States are now achieved by cesarean delivery, comprising more than 1.27 million women each year, national organizations have recently published revised guidelines for the management of labor. These new guidelines stipulate that labor arrest should not be diagnosed unless ≥6 cm cervical dilatation has been reached or labor has been stimulated for at ≥6 hours.
Objective
To determine the cervical dilatation and hours of labor stimulation prior to cesarean delivery for arrest of dilatation.
Materials and Methods
Between January 1, 1999, andDecember 31, 2000, a prospective observational study of all primary cesarean deliveries was conducted at 13 university centers comprising the Eunice Kennedy Shriver National Institute for Child Health and Human Development, Maternal-Fetal Medicine Units Network. This secondary analysis includes all live-born, singleton, nonanomalous, cephalic gestations delivered by primary cesarean delivery at ≥37 weeks. A cesarean delivery was considered to have been performed for arrest of dilatation if the indication for the procedure was failure to progress, cephalopelvic disproportion, or failed induction. Augmentation was defined as stimulation after spontaneous labor had been previously diagnosed. Analysis included both the latent and active phases of labor. The active phase of labor was diagnosed when cervical dilatation was ≥4 cm in the presence of uterine contractions.
Results
A total of 13,269 primary cesarean deliveries were available for analysis, 8,546 (65%) of which were performed for inadequate progress of labor with cervical dilatation recorded at the time of cesarean delivery. Of these cesarean deliveries for labor arrest, a total of 719 (8%) were performed in the latent phase of labor and 7827 (92%) were performed when cervical dilatation was ≥4 cm (active phase). Approximately two-thirds (n = =5876; 69%) received intrauterine pressure monitoring. A total of 5636 women (66% of those reaching the active phase of labor) had reached ≥6 cm cervical dilatation before cesarean delivery was performed. Moreover, 7440 (95%) of the 7827 women in active labor had ≥6 cm dilatation or had received labor stimulation ≥6 hours prior to cesarean delivery for arrest of dilatation.
Conclusion
Women undergoing primary cesarean delivery for arrest of dilatation 15 years before the recommendations of the Obstetrics Care Consensus had received bona fide efforts to achieve adequate labor consistent with the recommendations of the Consensus . Because 95% of these women had ≥6 cm dilatation or had received labor stimulation ≥6 hours prior to cesarean delivery for arrest of dilatation, these new recommendations are unlikely to change the cesarean delivery rates.
Nearly one-third of births, comprising more than 1.27 million women per year, are achieved by cesarean delivery in the United States. This represents an overall increase of approximately 40% from the national rate in 2000. National obstetric organizations have recently promulgated recommendations to reduce cesarean delivery rates, and specifically to reduce the rate of primary cesarean delivery. The primary cesarean delivery, that is, a first cesarean delivery regardless of the number of previous deliveries, has been the major focus of these efforts because such cesarean deliveries currently represent about 60% of the total performed in the United States. Both the 2009 Joint Commission on National Quality Core Measures for hospitals and the United States Department of Health and Human Services Healthy People 2010 established objectives specifically to reduce nulliparous, term, singleton, cephalic cesarean deliveries. A workshop sponsored by the Society for Maternal-Fetal Medicine (SMFM), the National Institute of Child Health and Human Development (NICHD), and the American College of Obstetricians and Gynecologists (ACOG) titled, “Preventing the First Cesarean Delivery” was convened in 2012 to address this issue. The recommendations from this workshop served as a nidus for change to labor management changes. Indeed, this workshop was an influence for re-defining labor management strategies and the subsequent publication in 2014 of the inaugural Obstetric Care Consensus titled “Safe Prevention of the Primary Cesarean Delivery” that was jointly endorsed by both the ACOG and SMFM. This Consensus document was reaffirmed in 2016.
Why was this study conducted?
Because national organizations have recently (2014) promulgated revised guidelines for the management of labor, we sought to chronicle labor management in women who had cesarean delivery for arrest of dilatation before the new labor management recommendations were available. Our purpose was to profile labor management prior to primary cesarean delivery for arrest of dilatation between 1 January 1999 and 31 December 2000 at 13 university centers in the United States.
Key findings
A total of 13,269 primary cesarean deliveries were available for analysis, 8,666 (65%) of which were performed for arrest of dilatation. Of these cesarean deliveries for labor arrest, 719 (8%) were performed in the latent phase of labor and 7827 (92%) were performed when cervical dilatation was ≥4 cm. A total of 5636 women (66% of those reaching the active phase of labor, defined as ≥4 cm) had reached ≥6 cm cervical dilatation before cesarean was performed. A total of 7440 women (95%) had ≥6 cm dilatation or had received labor stimulation ≥6 hours prior to cesarean delivery for arrest of progress.
What does this add to what is known?
Women undergoing primary cesarean delivery for failed labor 15 years before the recommendations of the Obstetrics Care Consensus had received bona fide efforts to achieve adequate labor consistent with the recommendations of the Consensus .
One of the recommendations by the Obstetric Care Consensus was that 6 cm cervical dilatation should be required as the new threshold for the diagnosis of active-phase labor. Furthermore, the consensus committee recommended that cesarean delivery for arrest of labor in the first stage should be performed only after ≥6 cm cervical dilatation had been achieved and should include membrane rupture and either ≥4 hours of adequate contractions or ≥6 hours for inadequate contractions. The rationale for this recommendation was based upon data supporting extension of the time necessary for active-phase labor arrest. For example, Rouse et al suggested that the previously recommended 2-hour minimum of adequate uterine activity prior to performing cesarean delivery was too short. It was suggested that a 4-hour minimum would safely result in fewer cesarean deliveries for failed labor.
There have been several reports published on labor management as now recommended by the Obstetric Care Consensus . For example, Rosenbloom et al examined primary cesarean delivery rates following ongoing adoption and implementation of the new labor management guidelines and found that the cesarean delivery rate was not reduced. Moreover, they found an increase in maternal and neonatal morbidity. This report of trends during 2010−2014 was stimulated, in part, by both the Obstetric Care Consensus as well as the findings of Zhang et al and the Consortium on Safe Labor published in 2010 analyzing labor curves in nulliparous women delivering vaginally with normal neonatal outcomes—ie. excluding cesarean deliveries and adverse neonatal outcomes. Such reports have led to the suspicion that the Obstetric Care Consensus was an effort to simply “do something” to alter the cesarean delivery rate. The consequence of such actions has been described as “ both ineffective and potentially harmful .” Because of this, we now ask whether these new recommendations were indeed novel.
In an effort to further examine issues related to cesarean delivery, the Eunice Kennedy Shriver National Institute for Child Health and Human Development Maternal-Fetal Medicine Units Network (NICHD MFMU) performed an observational study of primary cesarean deliveries between January 1, 1999 and December 31, 2000, at 13 university centers in the United States. Using data from this registry released to the public in March 2014, we sought to chronicle labor management practices in women who had cesarean delivery for arrest of dilatation before the Obstetric Care Consensus recommendations were promulgated. Our purpose was to assess the prevailing labor management practices prior to cesarean delivery for arrest of dilatation in 1999−2000.
Materials and Methods
Study design
This is a secondary analysis of the NICHD MFMU Network Cesarean Section Registry. Between January 1, 1999, and December 31, 2000, all women undergoing a primary cesarean delivery at the 13 participating university centers were prospectively ascertained. Detailed information regarding medical and obstetric history, intrapartum course to include labor management, postpartum complications, and infant outcomes were abstracted directly from maternal and infant charts by certified research nurses. Because these data are now available in the public domain, this analysis qualified for exempt status from the Institutional Review Board at the University of Texas Southwestern Medical Center. The cohort analyzed was limited to women with primary cesarean delivery at term who underwent cesarean delivery for inadequate progress of labor. Women missing cervical dilatation data were excluded. Our purpose was to determine how far labor had progressed before diagnosing failed labor and performing primary cesarean delivery in 1999−2000.
Labor analysis
Labor was analyzed throughout the first stage in accordance with the labor curves defined by Friedman before publication of the 2014 Consensus document. For this analysis, and as was used in contemporary practice during the years of this report, the first stage was divided into the latent and active phases. The latent phase was defined as 0−3 cm cervical dilatation, and the active phase was defined as 4 cm through complete dilatation of the cervix. A cesarean delivery was considered to have been performed for labor arrest (ie, arrest of dilatation) if the indication for the procedure was failure to progress, cephalopelvic disproportion, or failed induction. Failure to progress and cephalopelvic disproportion are commonly used interchangeably in clinical practice and included protraction or arrest in the active phase of labor. Failed induction included those women who underwent de novo stimulation of labor followed by cesarean delivery for failure to progress. Augmentation was defined as stimulation after spontaneous labor had been previously diagnosed.
Several variables were examined to determine at what point labor arrest was diagnosed. This included intrauterine pressure monitoring of contractions and the greatest number of Montevideo units (MVU) achieved. Briefly, MVUs are the peak amplitude of uterine contractions above baseline uterine tone multiplied by the number of contractions during a 10-minute period. We were especially interested in those women who achieved ≥200 MVUs.
Statistical analysis included the χ 2 test for dichotomous variables and the Student t test and Wilcoxon rank-sum test for continuous variables where appropriate. Nominal 2-sided P values are reported, with a P < .05 considered significant. SAS software, version 9.4 (SAS Institute, Cary, NC) was used for the analysis.
Results
Study population
A total of 23,491 women underwent primary cesarean delivery, and 13,269 of these had term, singleton, nonanomalous, cephalic live births ( Figure ). A total of 8546 (64%) had a primary cesarean delivery for inadequate progression of labor and are the focus of this analysis. The distribution of cervical dilatation at the time of cesarean delivery is also shown in Figure 1 . Demographics for these women are provided in Table 1 . A total of 719 cesarean deliveries (8%) were performed between 0 and 3 cm dilatation and therefore in the latent phase, and 631 (88%) of these were nulliparous. Of those women with cesarean deliveries in the latent phase, 677 (94%) received either induction or augmentation of labor. The median admission to delivery time for these latent-phase cesarean deliveries was 20.9 hours (13.0, 32.3; first and third quartiles, respectively).
