Objective
To describe contemporary cesarean delivery practice in the United States.
Study Design
Consortium on Safe Labor collected detailed labor and delivery information from 228,668 electronic medical records from 19 hospitals across the United States, 2002-2008.
Results
The overall cesarean delivery rate was 30.5%. The 31.2% of nulliparous women were delivered by cesarean section. Prelabor repeat cesarean delivery due to a previous uterine scar contributed 30.9% of all cesarean sections. The 28.8% of women with a uterine scar had a trial of labor and the success rate was 57.1%. The 43.8% women attempting vaginal delivery had induction. Half of cesarean for dystocia in induced labor were performed before 6 cm of cervical dilation.
Conclusion
To decrease cesarean delivery rate in the United States, reducing primary cesarean delivery is the key. Increasing vaginal birth after previous cesarean rate is urgently needed. Cesarean section for dystocia should be avoided before the active phase is established, particularly in nulliparous women and in induced labor.
Cesarean delivery has become the most common major surgical procedure in many parts of the world. The national rate of cesarean delivery in the United States has increased more than 50% since 1996 to 31.8% in 2007. This upward trajectory appears likely to continue in the near future.
For Editors’ Commentary, see Table of Contents
Reasons for the increase are multifaceted. Delayed childbearing, increasing maternal body mass, more multifetal gestations, and low use of vaginal birth after previous cesarean (VBAC) are commonly cited causes. Cesarean delivery on maternal request and physicians’ fear of litigation due to a poor obstetric outcome may also be contributing to the escalating rate of cesarean delivery. Despite anecdotal evidence and the common belief that certain cesarean deliveries may be unnecessary, the magnitude of unnecessary cesarean section at the national level is unknown. Reliable, detailed information on labor and delivery is often unavailable in a large population. Consequently, our understanding of the underlying causes of high cesarean rate is incomplete.
To meet this challenge, the Eunice Shriver Kennedy National Institute of Child Health and Human Development, National Institutes of Health, in collaboration with 12 institutions across the country, conducted a retrospective observational study entitled “the Consortium on Safe Labor.” The goal of the study was to collect comprehensive information on contemporary labor and delivery practice in multiple institutions. This paper describes the contemporary cesarean delivery practice in the US population.
Materials and Methods
The Consortium on Safe Labor included 12 clinical centers (with 19 hospitals) across 9 American College of Obstetricians and Gynecologists (ACOG) US districts. There were 8 university affiliated teaching hospitals, 9 teaching community hospitals, and 2 nonteaching community hospitals. They were chosen because of the availability of electronic medical records at each institution and because their geographic distribution covers all ACOG US districts. A total of 228,668 deliveries with 233,844 newborns between 2002 and 2008 were included in the study. Between 2005 and 2007, 87% births occurred. All births at 23 weeks or later in these institutions were included. A total of 9.5% of women contributed more than 1 delivery to the database. To avoid intraperson correlation, we selected the first delivery from each subject in the study, leaving 206,969 deliveries for analysis. Participating institutions extracted detailed information from their electronic medical records on maternal demographic characteristics, medical history, reproductive, and prenatal history, labor, and delivery summary, postpartum and newborn information. Information from the neonatal intensive care unit (NICU) was linked to the newborn records. Data on labor progression were extracted from the electronic labor database. Information on hospital and physician characteristics was collected from surveys of the local investigators, and maternal and newborn discharge summaries (in International Classification of Diseases-9 codes) were linked to each delivery. This project was approved by the institutional review boards of all participating institutions.
Data transferred from the clinical centers were mapped to predefined common codes for each variable at the data coordinating center. Data inquiries, cleaning, recoding, and logic checking were performed. We also conducted validation studies for 4 key outcome diagnoses, including cesarean for nonreassuring fetal heart rate tracing, asphyxia, NICU admission for respiratory conditions, and shoulder dystocia. To validate data, eligible charts were selected, and investigators were asked to recollect data with chart abstraction done by hand. We compared the information hand collected from the medical charts with that downloaded from the electronic medical records. Appendix Table 1 indicates that most variables that were reviewed in this study are highly accurate. Although our records were not sampled randomly, the consistency among different records on the same variable (eg, singleton, gestational age, attempting vaginal birth, live birth, vertex presentation) indicates that the information provided in the validation studies is reliable and likely to be generalizable to the entire database. Thus, the electronic medical records are a reasonably accurate representation of the medical charts.
Approximately 5.9% of women in our study had missing information on fetal presentation. Given the importance of fetal presentation in our analysis, we performed multiple imputation. A logistic regression model imputed the likelihood of vertex/nonvertex presentation in a particular subject multiple times based on other obstetric characteristics, including maternal race, parity, previous uterine scar, number of fetus, external cephalic version, smoking, placenta previa, cephalopelvic disproportion, gestational age, reason for admission to labor/delivery, trial of labor, induction, fetal scalp electrode, operative vaginal delivery, and mode of delivery. When the imputed data were analyzed, the uncertainty that was related to imputation was taken into account.
To make our study population reflect the overall US obstetric population and to minimize the impact of the various number of births from different institutions, we assigned a weight to each subject based on ACOG district, maternal race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, and others), parity (nulliparous vs multiparous), and plurality (singleton vs multiple gestation). We first calculated the probability of each delivery with these 4 factors according to the 2004 National Natality data ; publicly available National Natality data can no longer be separated by state after 2004. Then, based on the number of subjects each hospital contributed to the database, we assigned a weight to each subject. Appendix Table 2 indicates that the weighted study population is close to the entire US obstetric population. Therefore, we used the weighted sample throughout our analyses.
We defined “attempting vaginal delivery or a trial of labor” as all vaginal deliveries plus cesarean deliveries with at least 2 vaginal examination data in the labor progression (or labor curve) database. For indications for cesarean delivery, we first listed all major indications and the percent of cesarean deliveries with a specific indication (1 woman may have more than 1 indication). “Elective cesarean delivery” was defined as cesarean for clinical indications of: (1) elective as denoted in the electronic medical record, (2) declining a trial of labor, and (3) a variety of factors that are not considered accepted indications for cesarean delivery such as elderly gravida, multiparity, remote from term, postterm/postdates, diabetes, chorioamnionitis, chronic or gestational hypertension without preeclampsia/eclampsia, premature rupture of the membranes, human papillomavirus infection, Group B streptococcus positive, polyhydramnios, fetal demise, tubal ligation, and social/religion concerns. We then grouped all indications into 3 hierarchical, mutually exclusive categories: “clinically indicated,” “mixed,” and “truly elective.” The “mixed” group included cesarean deliveries where not enough detailed information (eg, human immunodeficiency virus with an unknown viral load or unknown presentation of twins) was available to judge the necessity or where the clinical indications were not that strong (eg, preeclampsia).
Duration of labor arrest was calculated as the duration of no appreciable change of cervical dilation in the first stage and the time interval between the first 10 cm and delivery in the second stage. “No appreciable change in cervical dilation” was defined as within 1 cm of change in dilation before delivery. All statistical analyses were performed using SAS version 9.1 (SAS Institute, Inc, Cary, NC). Given that this is a descriptive analysis with a very large sample size, no statistical testing was performed; nor were confidence intervals provided.
Results
The overall rate of cesarean delivery in our cohort was 30.5%, varying from 20% to 44% among the participating hospitals. Table 1 presents the overall and specific categories of cesarean delivery (primary vs repeat, and prelabor vs intrapartum) by maternal characteristics. With advancing maternal age, the overall cesarean rate doubled from 21.0% at age <20 years to 42% in women 35 years or older, mainly due to repeat, prelabor cesarean deliveries. Obesity was associated with substantially higher cesarean rates in all categories. One in 3 nulliparous women was delivered by cesarean section (31.2%). Multiparous women had an overall cesarean rate similar to that of nulliparous women (30.0%), primarily due to prelabor, repeat cesarean delivery.
| Variable | Proportion of the population, % | Overall cesarean rate, a % | Primary cesarean delivery, a % | Repeat cesarean delivery, a % | Prelabor cesarean delivery, a % | Intrapartum cesarean delivery, a % |
|---|---|---|---|---|---|---|
| n (unweighted) | 206,969 | 60,866 | 38,336 | 22,530 | 32,380 | 28,486 |
| n (weighted) | 3,997,436 | 1,220,877 | 727,941 | 492,935 | 696,583 | 524,294 |
| Maternal age, y | ||||||
| <20 | 8.6 | 21.0 | 18.8 | 2.2 | 6.6 | 14.5 |
| 20-24 | 22.6 | 24.6 | 16.5 | 8.1 | 11.7 | 12.9 |
| 25-29 | 27.0 | 28.1 | 16.6 | 11.5 | 15.9 | 12.3 |
| 30-34 | 24.7 | 33.6 | 18.9 | 14.9 | 20.6 | 13.2 |
| 35+ | 17.2 | 42.2 | 21.7 | 20.5 | 28.3 | 14.0 |
| Race/ethnicity | ||||||
| Non-Hispanic white | 56.6 | 29.9 | 18.3 | 11.6 | 17.8 | 12.1 |
| Non-Hispanic black | 14.2 | 33.4 | 20.5 | 13.2 | 17.4 | 16.3 |
| Hispanic | 22.9 | 30.3 | 16.5 | 13.8 | 16.9 | 13.4 |
| Asian/Pacific Islanders | 3.2 | 30.6 | 19.6 | 11.1 | 15.5 | 15.2 |
| Other | 3.1 | 29.3 | 17.4 | 11.8 | 17.2 | 12.1 |
| Health insurance | ||||||
| Private | 53.5 | 31.3 | 19.3 | 12.0 | 17.9 | 13.4 |
| Public | 33.3 | 31.6 | 18.1 | 13.6 | 17.9 | 13.8 |
| Other/unknown | 13.2 | 24.6 | 14.0 | 10.6 | 14.2 | 10.3 |
| Body mass index at delivery, kg/m 2 | ||||||
| <25 | 13.5 | 22.3 | 14.0 | 8.4 | 13.8 | 8.6 |
| 25.0-29.9 | 37.7 | 25.6 | 15.8 | 9.8 | 14.5 | 11.1 |
| 30.0-34.9 | 27.6 | 32.6 | 19.3 | 13.3 | 18.4 | 14.3 |
| 35.0+ | 21.2 | 43.7 | 24.6 | 19.2 | 25.0 | 18.8 |
| Parity | ||||||
| Nulliparous | 40.4 | 31.2 | 31.2 | 0.1 | 9.7 | 21.5 |
| Multiparous | 59.6 | 30.0 | 9.4 | 20.6 | 22.7 | 7.4 |
| Number of fetuses | ||||||
| Singleton | 98.3 | 29.9 | 17.7 | 12.2 | 16.9 | 13.1 |
| Multiple | 1.7 | 65.9 | 47.0 | 18.9 | 50.6 | 15.3 |
| Labor induction in women attempting vaginal delivery | ||||||
| No | 56.2 | 11.8 | 9.1 | 2.7 | 0 | 11.8 |
| Yes | 43.8 | 21.1 | 19.5 | 1.6 | 0 | 21.1 |
| Previous uterine scar | ||||||
| No | 84.9 | 21.1 | 21.1 | 0 | 7.8 | 13.2 |
| Yes | 15.1 | 83.6 | 2.2 | 81.4 | 71.3 | 12.3 |
| Vertex presentation (singleton only) | ||||||
| No | 5.1 | 92.8 | 71.1 | 21.6 | 73.8 | 19.0 |
| Yes | 94.9 | 26.6 | 14.9 | 11.7 | 13.8 | 12.8 |
| Hospital type | ||||||
| University affiliated teaching hospital | 60.7 | 32.9 | 19.4 | 13.5 | 19.5 | 13.5 |
| Teaching community Hospital | 35.9 | 27.2 | 16.7 | 10.5 | 14.5 | 12.8 |
| Nonteaching community hospital | 3.4 | 23.1 | 12.8 | 10.4 | 12.6 | 10.5 |
a Overall cesarean rate = primary + repeat cesarean rates = prelabor + intrapartum cesarean rates. Repeat cesarean section includes cesarean section after previous myomectomy in nulliparous women (0.1%).
A total of 65.9% multifetal gestations were delivered by cesarean section (in comparison to 29.9% in singleton pregnancies), and a majority of multifetal gestations did not attempt vaginal delivery. The induction rate was 36.2%, using all deliveries as the denominator, or 43.8% among women attempting vaginal delivery. The cesarean rate was twice as high in induced labor than in spontaneous labor in all pregnancies (21.1% vs 11.8%) and in singleton nulliparous women with vertex presentation (31.4% vs 14.2%). In women with a previous uterine scar, 28.8% had a trial of labor. Among them, the rate of successful VBAC was 57.1%. Overall, 83.6% of women with a uterine scar were delivered by cesarean section. A total of 92.8% fetuses with nonvertex presentation were delivered by cesarean section.
To further examine the relative contribution of obstetric factors to the cesarean rate, we grouped the women into 7 categories according to the classification scheme proposed by Robson. Table 2 indicates that term pregnancies with a vertex, singleton fetus, and previous uterine scar contributed the most cesarean deliveries in the United States (30.9%), followed by term gestations with a singleton, vertex fetus whose labor was induced (19.2%). Multifetal gestations and pregnancies with nonvertex presentation accounted for only 6.7% of all births but contributed to one-fifth of all cesarean deliveries.
| Robson classification a | Obstetric characteristics | Proportion of all deliveries, % | Rate of prelabor cesarean delivery, % | Rate of intrapartum cesarean delivery, % | Proportion of all cesarean deliveries, % |
|---|---|---|---|---|---|
| 1 | Nulliparous, singleton, vertex, ≥37 wk, spontaneous labor | 16.5 | — | 14.8 | 8.0 |
| 3 | Multiparous, singleton, vertex, ≥37 wk, no uterine scar, spontaneous labor | 20.9 | — | 3.1 | 2.1 |
| 2a + 4a | All women, singleton, vertex, ≥37 wk, no uterine scar, induced labor | 30.9 | — | 19.0 | 19.2 |
| 2b + 4b | All women, singleton, vertex, ≥37 wk, no uterine scar, prelabor cesarean delivery | 2.4 | 100 | — | 7.9 |
| 5 | All women, singleton, vertex, ≥37 wk, uterine scar | 11.5 | 70.2 | 11.8 | 30.9 |
| 10 | All women, singleton, vertex, <37 wk, regardless uterine scar | 11.1 | 21.5 | 14.2 | 13.0 |
| 6 + 7 + 8 + 9 | All women, multiple gestation or nonvertex presentation, regardless uterine scar | 6.7 | 67.7 | 17.9 | 18.8 |
| Overall | 100% | 100% |
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