- Email: [email protected]
Epidemiology of Cesarean Delivery: The Scope of the Problem
Epidemiology of Cesarean Delivery: The Scope of the Problem Annelee Boyle, MD,* and Uma M. Reddy, MD, MPH† Approximately one-third of births in the United States are via cesarean delivery (CD). The rate of CD has increased dramatically since the 1990s, reaching a peak of 32.9% in 2009. The increase can be seen among women of all ages and race/ethnicities, in every state, and across all gestational ages. The primary CD rate has increased from 14.5% in 1996 to 23.4% in 2007. Because the primary CD rate has increased and the rate of trial of labor after CD has decreased, the primary cesarean rate has become a major driver in the total CD rate. Also contributing to the high CD rate is an increase in somewhat subjective indications, such as fetal distress or nonreassuring fetal tracing and failure to progress leading to performance of CD in the latent phase of labor. Addressing these factors—as well as focusing on the use of elective induction and management of early labor in the particular subgroup of nulliparous women at term, with singleton fetuses in vertex presentation—may have a significant impact on the total CD rate. Semin Perinatol 36:308-314 Published by Elsevier Inc. KEYWORDS primary cesarean delivery, epidemiology, indications
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lthough it is unlikely that Julius Caesar was actually born via the procedure that bears his name, cesarean delivery (CD) has been described for more than 2000 years.1 It is the most common major surgery in the United States, reaching an all-time high of 32.9% of all US births in 2009.2,3 In February 2012, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Society for Maternal Fetal Medicine, and the American College of Obstetricians and Gynecologists cosponsored a workshop on preventing the first CD. This article is a review of the epidemiology of and primary contributors to the increased CD rate in the United States. The following definitions are used to determine CD rates and monitor trends in CD. The total cesarean rate is the percentage of CDs out of all births in a given year.4 The primary cesarean rate is the percentage of CDs out of all births to women who have not had a previous CD.4 The
*Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Washington Hospital Center, Washington, DC. †Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD. Address reprint requests to Uma M. Reddy, MD, MPH, Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 6100 Executive Boulevard Room 4B03F, Bethesda, MD 20892-7510. E-mail: [email protected]
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repeat cesarean rate is the percentage of CDs out of all births to women who have had a previous CD.4 Related to the repeat cesarean rate is the vaginal birth after cesarean delivery (VBAC) rate, which is the percentage of vaginal births out of all births to women who have had a previous CD.4 The repeat cesarean rate plus the VBAC rate equals 100% for the group of women delivering with a history of a previous CD.
National CD Trends The total cesarean rate in the United States has increased dramatically since the 1990s. Figure 1 shows the total CD rate in the United States from 1990 to 2010. After a small dip in the early 1990s, to a low of 20.7% in 1996, the total cesarean rate rose steadily from 1996 to 2009.3 Preliminary data for 2010 show a slight drop in the total cesarean rate— from 32.9% of deliveries in 2009 to 32.8% in 2010, the first decrease in the rate in more than a decade.3,5 However, CD is still the most common major surgery performed in the United States and affects 1.3 million women per year.2,6 Since 1996, the United States total cesarean rate has increased by almost 60%.6 The decline in total cesarean rate between 1990 and 1996 was because of decreases in both the primary cesarean rate and the repeat cesarean rate.4 Since 1996, the United States total, primary, and repeat cesarean rates have all increased, and the VBAC rate has decreased (Fig. 1).4,6 National primary
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Figure 1 Total cesarean, primary cesarean, and vaginal birth after cesarean delivery rates: USA, 1990-2010.3,5,6 *Rate represents percentage of cesarean deliveries (CDs) out of all births in a given year. †Rate represents percentage of cesarean deliveries out of all births to women who have not had a previous CD. ‡Rate represents percentage of vaginal births out of all births to women with a previous CD. (Color version of figure is available online.)
and repeat cesarean rates can be quantified through 2004.4,7 Since 2005, it has not been possible to produce comparable national estimates because of revisions in states’ birth certificate data collection.4,7 Subnational estimates are available, but they must be used with caution. For example, 2007 data for primary and repeat CDs are available for 22 states.4,7 Although the data represent 53% of US births, the data are not directly generalizable to the United States as a whole because births in the 22-state area are not a random sample of all US births.4,7 Births to Mexican women are overrepresented in the data, whereas births to non-Hispanic white and non-Hispanic black women are underrepresented.4,7 Recognizing this limitation, it is still valuable to examine trends in primary and repeat cesarean rates using the data that are available. Figure 2 shows primary cesarean rates for
30
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the United States as a whole and for the 22-state reporting area. The national primary cesarean rate was 14.6% in 1996 and 20.6% in 2004, an increase of 41%.4 During the same period, the primary cesarean rate for the 22-state area climbed from 14.5% to 21.1%, an increase of 46%.4 The primary cesarean rate for the 22-state area rose to 23.4% in 2007, an increase of 61% from 1996.4 Figure 3 shows VBAC rates for the United States as a whole and for the 22-state reporting area. The national VBAC rate peaked at 28.3% in 1996 and then dropped sharply to 9.2% in 2004, a decrease of 67%.4 The VBAC rate for the 22-state area also plummeted during this period, from 27.3% in 1996 to 8.6% in 2004, a 68% drop.4 By 2007, the VBAC rate for the 22-state reporting area had declined further, to 8.3%.4 For the 22-state area, the total decrease in VBAC rate from 1996
22-State Reporting Area 23.4 21.1
20.6
20 14.6
14.5
10
0 1996
2004
2007
Source: MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011
Figure 2 Primary CD rates: United States and 22-state reporting area, 1996, 2004, and 2007.4 (Color version of figure is available online.)
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28.3
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27.3
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9.2
10
8.6
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0 1996
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2007
Source: MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011
Figure 3 Vaginal birth after cesarean delivery rates: United States and 22-state reporting area, 1996, 2004, and 2007.4 (Color version of figure is available online.)
to 2007 was 70%.4 Recognizing the decline in VBACs since the 1990s, American College of Obstetricians and Gynecologists revised its practice bulletin on vaginal birth after previous CD in 2010, expanding the eligibility criteria with the hope of increasing the VBAC rate.8 The percentage of births to women with a previous CD is helpful in demonstrating the effects of rising CD rates on a population as a whole.4 During the 1990s, this percentage was relatively stable nationally, staying between 10.5% and 10.8%; by 2004, it had increased to 12.1%.4 In the 22-state reporting area, this percentage was 10.8% in 1996, 12.0% in 2004, and 12.9% in 2007; the total increase in the 22-state reporting area from 1996 to 2007 was nearly 20%.4 The rise in CDs can be seen among all ages and races, in every state, and across all gestational ages. CD rates increased among women in all age groups from 1996 to 2009, according to birth data from the Centers for Disease Control and Prevention National Center for Health Statistics (CDC/ NCHS) (Fig. 4).3 Every age group had an increase of at least
50
1996
50%.3 Women aged 20-24 had the largest increase at 64%.3 In 1996 and 2009, the cesarean rate for mothers aged 40-54 years was more than twice the rate for mothers under age 20, illustrating that the cesarean rate increases with advancing maternal age.3 The CDC/NCHS birth data also show that all racial and ethnic groups experienced increases of at least 50% in CD rates from 1996 to 2009 (Fig. 5).6 In 2009, CD rates were highest among non-Hispanic black women (35%) and lowest among American Indian or Alaska Native women (28%).6 Preliminary data for 2010 show that the total CD rate for non-Hispanic black women was 35.5%, for non-Hispanic white women it was 32.6%, and for Hispanic women it was 31.8%.5 CD rates have also increased across gestational age. Rates are the highest at earlier gestational ages. Using 2009 CDC/ NCHS birth data, the CD rate was 54% for early preterm births (⬍34 weeks’ gestation), 42% for late preterm births (34-36 weeks’ gestation), and 31% for term births (⬎37
46.7
2009 40.6
40 34.4 30.3
30
30.2
27.4
26.1 22.6
22.3 19.6
20
16.7 13.9
10
0 Under 20
20–24
25–29
30–34
35–39
40–54
Source: Martin JA, Hamilton BE, Ventura SJ, et al. Births: Final data for 2009. National vital statistics reports; vol 60 no 1. Hyattsville, MD: National Center for Health Statistics. 2011.
Figure 4 CD rates, by age of mother: United States, 1996 and 2009.6,9 (Color version of figure is available online.)
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35
2009 33
33
32
30
28 22
21 19
20
20 18
10
0 Non-Hispanic black
Non-Hispanic white
Asian or Pacific Islander
Hispanic
American Indian or Alaska Native
Sources: 1996 Data from Menacker F, Hamilton BE: Recent trends in cesarean delivery in the United States. NCHS Data Brief 35:1-8, 2010 2009 Data calculated from Center for Disease Control and Prevention. National Center for Health Statistics. VitalStats. National Vital Statistics System. http://www.cdc.gov/nchs/vitalstats.htm
Figure 5 CD rates, by race and Hispanic origin of mother: United States, 1996 and 2009.3,9 (Color version of figure is available online.)
weeks’ gestation).6 Between 1996 and 2006, the cesarean rate increased by 36% for early preterm deliveries and by almost 50% for late preterm and term deliveries.9 There is large variation in CD rates across the United States (Fig. 6).3 In 2009, total cesarean rates ranged from a low of ⬍25% in 4 states (Alaska, Idaho, New Mexico, and Utah) to a high of ⬎35% in 11 states (Alabama, Connecticut, Delaware, Florida, Kentucky, Louisiana, Mississippi, New Jersey, South Carolina, Texas, and West Virginia).3 Louisiana had the highest rate (39.6%).3 Every state and the District of Columbia experienced a significant rise between 1996 and 2009 (Fig. 7).3,9 Forty-three states and the District of Columbia had increases of at least 50%; 9 states had increases of 70% or more.3,9 Rhode Island had the largest increase (85%).3,9
International CD Trends The United States CD rate is relatively higher than that of other industrialized nations’. Among the 30 countries that provided data to the Organisation for Economic Co-operation and Development in 2008, CD rates ranged from a low of 14.3% for the Netherlands to a high of 43.9% for Mexico (Fig. 8).10 The total CD rate in the United States was higher than the rate for 24 of the other 29 countries.10 Compared with the United States cesarean rate, the Canadian rate was 18% lower, the rate for the United Kingdom was 28% lower, the French rate was 38% lower, and the Dutch rate was 56% lower.10 High rates of CD also affect Latin America. Taljaard and colleagues11 examined the CD rates for 120 institutions in 8 countries in Latin America. The overall CD rate was
Figure 6 Cesarean rate by state: United States, 2009.3 (Color version of figure is available online.)
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Figure 7 Percent increase in cesarean rates by state: United States, 1996-2009.3,9 (Color version of figure is available online.)
35%, but the range among institutions was 0%-85%. Even after risk adjustment, CD rates ranged from 11% to 78%.11 The authors found that characteristics of institutions explained 48% of the variability among risk-adjusted rates.11 These characteristics included being a private as opposed to a public institution, having some economic incentive for CD as opposed to no incentive, and having ⬎50 maternity beds.11 Hanley et al12 also found marked variations in CD rates in British Columbia. Reviewing all deliveries from 2004 to 2007, they found that the rate of primary CD varied from
Netherlands Iceland Finland Denmark Sweden Slovenia Norway Israel Poland France Estonia Czech Republic New Zealand United Kingdom Spain Slovak Republic Ireland Canada Austria Germany Luxembourg Australia Hungary Switzerland United States Portugal Korea Turkey Italy Mexico
16.1% to 27.5%, whereas assisted vaginal delivery rates varied from 8.6% to 18.6%.12 After controlling for maternal characteristics and conditions known to increase the likelihood of CD and assisted vaginal delivery, rates still varied 2-fold.12 Adjusted CD rates ranged from 14.7% to 27.6%, and adjusted assisted vaginal delivery rates ranged from 6.5% to 15.3%.12 The authors found that there was substantial regional variation in the use of CD, which could not be explained by patient illness or preferences.12 They concluded that this variation likely reflected differences in practitioners’ approaches to medical decision-making.12
14.3 16.1 16.5 16.6 16.8 17.0 17.1 18.8 19.3 19.9 20.0 20.5 22.8 23.4 24.6 24.7 25.6 26.6 27.5 29.4 30.2 30.8 31.4 31.6 32.3 32.7 35.4 37.7 38.5 43.9
0.0
10.0
20.0
30.0
40.0
50.0
Source: Organisation for Economic Co-operation and Development. OECD Health Data 2011- Frequently Requested Data. http://www.oecd.org/document/16/0,3746,en_2649_33929_2085200_1_1_1_1,00.html
Figure 8 Percentage of cesarean births: Organisation for Economic Co-operation and Development countries, 2008.10 (Color version of figure is available online.)
Epidemiology of primary cesarean delivery In 2009, Brennan and colleagues13 examined 9 institutional cohorts, each from a different country. They classified each pregnancy using Robson’s14 10-group system based on characteristics of the pregnancy: single versus multiple gestation, nulliparity versus multiparity with or without a previous CD, spontaneous versus induced labor, earlier or later than 37 weeks’ gestation, and fetal presentation. They found that breech, multiple gestations, and preterm deliveries were a fairly constant proportion of each population and contributed relatively little to overall CD rates.13 Instead, overall CD rates correlated with CD rates in nulliparous women at term with a single fetus with cephalic presentation; CD in this population explained 98% of interinstitutional variation in overall CD rate.13 In this study, TSCN (term, singleton, cephalic, nulliparous) women contributed an average of 34% to overall CD rates.13 The authors pointed out that this is a low-risk cohort amenable to effective intrapartum corrective intervention.13 In a different study, Brennan et al15 compared the TSCN cesarean rate with the overall cesarean rate in a single large institution in Ireland over a 35-year period. They found that, between 1974 and 2008, the overall cesarean rate increased from 5% to 19.1% and the TSCN cesarean rate increased from 4.4% to 15.8%.15 TSCN inductions increased from 19.7% to 32.7%, and the intrapartum cesarean rate in TSCN inductions rose from 4.1% to 27.3%.15 Institutional CD rates correlated with TSCN cesarean rates throughout the 35-year period.15 The authors estimated that 97% of the variation in overall institutional CD rates for the 35 years could be explained by the TSCN CD rate.15
Reasons for Increased CD Rates Barber et al16 looked at indications for CD at a single academic hospital between 2003 and 2009. They found that the CD rate increased from 26% to 36.5% during this period, and that 50% of the increase was attributable to an increase in primary CD.16 The relative contributions of each indication to the total increase in primary cesarean rate were nonreassuring fetal status (32%), labor arrest disorders (18%), multiple gestation (16%), suspected macrosomia (10%), preeclampsia (10%), maternal request (8%), maternal-fetal conditions (5%), and other obstetrical conditions (1%).16 Like Brennan, Main et al17 found large variation in management of the TSCN delivery in their cohort study of 20 birthing units in California. Strong correlations were found between CD rates and labor induction rates as well as CD rates and early labor admission rates.17 The strongest correlation was found between TSCN CD rates and a combined measure of induction and early labor admission; 53% percent of the interhospital variation in CD rate could be explained by these 2 practices.17 They concluded that the TSCN cesarean rate was strongly influenced by these elective obstetrical practices.17 In a retrospective cohort study of CD among 7804 TSCN women at a single large institution, Ehrenthal et al18 found that labor induction was used in 43.6% of cases, 39.9% of which were elective. Use of labor induction was associated
313 with increased odds of CD, and the association remained significant after adjustment for maternal demographic characteristics, medical risk, and pregnancy complications (adjusted odds ratio 1.93, 1.71-2.2).18 The contribution of labor induction to CD in the TSCN cohort was approximately 20%.18 Among TSCN women undergoing labor induction, 40.7% underwent cervical ripening, indicating a Bishop Score of ⬍6; among TSCN women with an elective indication, 37% had an unfavorable cervix.18 Indications for CD were labor dystocia in 75.1% of cases, fetal distress in 28.2%, maternal medical indications in 1.6%, and “other” indications in 2.9%.18 The risk factors that contributed most to CD in this population were labor induction and maternal obesity before pregnancy.18 The Consortium on Safe Labor (CSL) collected labor and delivery information from 228,668 electronic medical records from 19 hospitals across the United States from 2002 to 2008.19 The overall CD rate was 30.5%, but rates among institutions ranged from 20% to 44%.19 Of women attempting vaginal delivery, 43.8% were induced.19 The CD rate for induced labor was roughly double that of spontaneous labor in all pregnancies (21.1% vs 11.8%) and in TSCN women (31.4% vs 14.2%).19 Half of CDs for dystocia in induced labor were performed before 6 cm of cervical dilation.19 Among intrapartum CDs, approximately half were performed for “failure to progress” or “cephalopelvic disproportion,” and more than a quarter were performed for indications of “nonreassuring fetal testing” or “fetal distress.”19 One-third of CDs at the second stage were performed at ⬍3 hours in nulliparous women, whereas a quarter were performed at ⬍2 hours in multiparous women.19 Using contemporary data, the CSL developed new labor curves based on 62,415 parturients with a singleton term gestation, spontaneous onset of labor, a vertex presentation, vaginal delivery, and a normal perinatal outcome.20 Based on the Friedman labor curves, which were designed ⬎50 years ago, active phase labor is typically believed to start at 4 cm dilation.21 Appropriate labor progression in the active phase has been defined as cervical dilation of at least 1.2 cm/h in nulliparous women and at least 1.5 cm/h in multiparous women.21 No change in cervical dilation in the presence of adequate uterine contractions for ⬎2 hours is typically considered labor arrest.22 However, the CSL labor curves showed that progress from 4 to 6 cm was far slower than previously described.20 In fact, the rate of cervical dilation accelerated after 6 cm dilation, suggesting that 6 cm should be considered the start of the active phase of labor.20 Allowing labor to continue for a longer period before 6 cm of cervical dilation may potentially reduce the rate of intrapartum CDs, which would have a substantial effect on the total CD rate.
Conclusions Since 1996, the total CD rate in the United States has increased significantly among women of all ages, races, gestational ages, and in every state. The increase in the total CD rate has been paralleled by an increase in the primary CD rate. Based on the data, several factors need to be addressed to
314 decrease the primary CD rate. First, improved diagnosis of clinically accepted indications for CD is needed because the leading indications—“failure to progress,” “cephalopelvic disproportion,” “nonreassuring fetal testing,” and “fetal distress”—are somewhat subjective. Second, a high rate of labor induction is associated with an increased CD rate in nulliparous women, so addressing elective inductions in nulliparous women may have a substantial impact on CD rates. Third, a substantial proportion of CDs for failure to progress may be avoided if practitioners wait for the active phase of labor to commence, which appears to be at 6 cm dilation. Hospital-level data show that the large variation in management of TSCN births contributes significantly to the increased total cesarean rate. Recognizing the role that TSCN CD plays in the overall CD rate, one of the objectives of the US Department of Health and Human Services’ Healthy People 2020 initiative is to reduce cesarean births among lowrisk (full-term, singleton, vertex presentation) women giving birth for the first time by 10%—from 26.5% in 2007 to 23.9% in 2020.23 Targeting the labor management of this particular subgroup of women has the potential to make a sizable impact on the overall cesarean rate in the United States.
References 1. Boley JP: The history of caesarean section. 1935. CMAJ 145:319-322, 1991 2. Hall MJ, DeFrances CJ, Williams SN, et al: National Hospital discharge survey: 2007 summary. Natl Vital Stat Rep 29:1-24, 2010 3. Martin JA, Hamilton BE, Ventura SJ, et al: Births: Final data for 2009. Natl Vital Stat Rep 60:1-35, 2011 4. MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011 5. Hamilton BE, Martin JA, Ventura SJ: Births: Preliminary data for 2010. Natl Vital Stat Rep 60:1-14, 2011 6. Center for Disease Control and Prevention, National Center for Health Statistics: VitalStats. National Vital Statistics System. Available at: http://www.cdc.gov/nchs/vitalstats.htm. Accessed March 5, 2012 7. Center for Disease Control and Prevention, National Center for Health Statistics: User’s Guide to the 2007 Natality Public Use File. Available at: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/ DVS/natality/UserGuide2007.pdf. Accessed March 5, 2012
A. Boyle and U.M. Reddy 8. American College of Obstetricians and Gynecologists: ACOG Practice Bulletin no. 115: Vaginal birth after previous Cesarean delivery. Obstet Gynecol 116:450-463, 2010 9. Menacker F, Hamilton BE: Recent trends in cesarean delivery in the United States. NCHS Data Brief 35:1-8, 2010 10. Organisation for Economic Co-operation and Development: Health Data 2011—Frequently Requested Data. Available at: http://www. oecd.org/document/16/0,3746,en_2649_33929_2085200_1_1_1_1,00. html. Accessed February 28, 2012 11. Taljaard M, Donner A, Villar J, et al: Understanding the factors associated with differences in caesarean section rates at hospital level: The case of Latin America. Paediatr Perinat Epidemiol 23:574-581, 2009 12. Hanley GE, Janssen PA, Greyson D: Regional variation in the cesarean delivery and assisted vaginal delivery rates. Obstet Gynecol 115:12011208, 2010 13. Brennan DJ, Robson MS, Murphy M, et al: Comparative analysis of international cesarean delivery rates using 10-group classification identifies significant variation in spontaneous labor. Am J Obstet Gynecol 201:e1-e8, 2009 14. Robson M: Classification of caesarean sections. Fetal Matern Med Rev 12:23-39, 2001 15. Brennan DJ, Murphy M, Robson MS, et al: The singleton, cephalic, nulliparous woman after 36 weeks of gestation: Contribution to overall cesarean delivery rates. Obstet Gynecol 117:273-279, 2011 16. Barber EL, Lundsberg LS, Belanger K, et al: Indications contributing to the increasing cesarean delivery rate. Obstet Gynecol 118:29-38, 2011 17. Main EK, Moore D, Farrell B, et al: Is there a useful cesarean birth measure? Assessment of the nulliparous term singleton vertex cesarean birth rate as a tool for obstetric quality improvement. Am J Obstet Gynecol 194:1644-1651, 2006 18. Ehrenthal DB, Jiang X, Strobino DM: Labor induction and the risk of a cesarean delivery among nulliparous women at term. Obstet Gynecol 116:35-42, 2010 19. Zhang J, Troendle J, Reddy UM, et al: Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 203:e1-e10, 2010 20. Zhang J, Landy HJ, Branch DW, et al: Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116: 1281-1287, 2010 21. Kilpatrick S, Garrison E: Normal labor and delivery, in Gabbe SG, Niebyl JR, Simpson JL (eds): Obstetrics: Normal and Problem Pregnancies, 5th ed. Philadelphia, PA, Churchill Livingstone, 2007, p 314 22. Battista LR, Wing DA: Abnormal labor and induction of labor, in Gabbe SG, Niebyl JR, Simpson JL (eds): Obstetrics: Normal and Problem Pregnancies, 5th ed. Philadelphia, PA, Churchill Livingstone, 2007, p 325 23. US Department of Health and Human Services: 2020 Topics and Objectives, Maternal Infant and Child Health. Available at: http:// healthypeople.gov/2020/topicsobjectives2020/objectiveslist.aspx? topicId⫽26. Accessed March 4, 2012
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lthough it is unlikely that Julius Caesar was actually born via the procedure that bears his name, cesarean delivery (CD) has been described for more than 2000 years.1 It is the most common major surgery in the United States, reaching an all-time high of 32.9% of all US births in 2009.2,3 In February 2012, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Society for Maternal Fetal Medicine, and the American College of Obstetricians and Gynecologists cosponsored a workshop on preventing the first CD. This article is a review of the epidemiology of and primary contributors to the increased CD rate in the United States. The following definitions are used to determine CD rates and monitor trends in CD. The total cesarean rate is the percentage of CDs out of all births in a given year.4 The primary cesarean rate is the percentage of CDs out of all births to women who have not had a previous CD.4 The
*Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Washington Hospital Center, Washington, DC. †Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD. Address reprint requests to Uma M. Reddy, MD, MPH, Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 6100 Executive Boulevard Room 4B03F, Bethesda, MD 20892-7510. E-mail: [email protected]
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repeat cesarean rate is the percentage of CDs out of all births to women who have had a previous CD.4 Related to the repeat cesarean rate is the vaginal birth after cesarean delivery (VBAC) rate, which is the percentage of vaginal births out of all births to women who have had a previous CD.4 The repeat cesarean rate plus the VBAC rate equals 100% for the group of women delivering with a history of a previous CD.
National CD Trends The total cesarean rate in the United States has increased dramatically since the 1990s. Figure 1 shows the total CD rate in the United States from 1990 to 2010. After a small dip in the early 1990s, to a low of 20.7% in 1996, the total cesarean rate rose steadily from 1996 to 2009.3 Preliminary data for 2010 show a slight drop in the total cesarean rate— from 32.9% of deliveries in 2009 to 32.8% in 2010, the first decrease in the rate in more than a decade.3,5 However, CD is still the most common major surgery performed in the United States and affects 1.3 million women per year.2,6 Since 1996, the United States total cesarean rate has increased by almost 60%.6 The decline in total cesarean rate between 1990 and 1996 was because of decreases in both the primary cesarean rate and the repeat cesarean rate.4 Since 1996, the United States total, primary, and repeat cesarean rates have all increased, and the VBAC rate has decreased (Fig. 1).4,6 National primary
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Figure 1 Total cesarean, primary cesarean, and vaginal birth after cesarean delivery rates: USA, 1990-2010.3,5,6 *Rate represents percentage of cesarean deliveries (CDs) out of all births in a given year. †Rate represents percentage of cesarean deliveries out of all births to women who have not had a previous CD. ‡Rate represents percentage of vaginal births out of all births to women with a previous CD. (Color version of figure is available online.)
and repeat cesarean rates can be quantified through 2004.4,7 Since 2005, it has not been possible to produce comparable national estimates because of revisions in states’ birth certificate data collection.4,7 Subnational estimates are available, but they must be used with caution. For example, 2007 data for primary and repeat CDs are available for 22 states.4,7 Although the data represent 53% of US births, the data are not directly generalizable to the United States as a whole because births in the 22-state area are not a random sample of all US births.4,7 Births to Mexican women are overrepresented in the data, whereas births to non-Hispanic white and non-Hispanic black women are underrepresented.4,7 Recognizing this limitation, it is still valuable to examine trends in primary and repeat cesarean rates using the data that are available. Figure 2 shows primary cesarean rates for
30
United States
the United States as a whole and for the 22-state reporting area. The national primary cesarean rate was 14.6% in 1996 and 20.6% in 2004, an increase of 41%.4 During the same period, the primary cesarean rate for the 22-state area climbed from 14.5% to 21.1%, an increase of 46%.4 The primary cesarean rate for the 22-state area rose to 23.4% in 2007, an increase of 61% from 1996.4 Figure 3 shows VBAC rates for the United States as a whole and for the 22-state reporting area. The national VBAC rate peaked at 28.3% in 1996 and then dropped sharply to 9.2% in 2004, a decrease of 67%.4 The VBAC rate for the 22-state area also plummeted during this period, from 27.3% in 1996 to 8.6% in 2004, a 68% drop.4 By 2007, the VBAC rate for the 22-state reporting area had declined further, to 8.3%.4 For the 22-state area, the total decrease in VBAC rate from 1996
22-State Reporting Area 23.4 21.1
20.6
20 14.6
14.5
10
0 1996
2004
2007
Source: MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011
Figure 2 Primary CD rates: United States and 22-state reporting area, 1996, 2004, and 2007.4 (Color version of figure is available online.)
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28.3
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27.3
20
9.2
10
8.6
8.3
0 1996
2004
2007
Source: MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011
Figure 3 Vaginal birth after cesarean delivery rates: United States and 22-state reporting area, 1996, 2004, and 2007.4 (Color version of figure is available online.)
to 2007 was 70%.4 Recognizing the decline in VBACs since the 1990s, American College of Obstetricians and Gynecologists revised its practice bulletin on vaginal birth after previous CD in 2010, expanding the eligibility criteria with the hope of increasing the VBAC rate.8 The percentage of births to women with a previous CD is helpful in demonstrating the effects of rising CD rates on a population as a whole.4 During the 1990s, this percentage was relatively stable nationally, staying between 10.5% and 10.8%; by 2004, it had increased to 12.1%.4 In the 22-state reporting area, this percentage was 10.8% in 1996, 12.0% in 2004, and 12.9% in 2007; the total increase in the 22-state reporting area from 1996 to 2007 was nearly 20%.4 The rise in CDs can be seen among all ages and races, in every state, and across all gestational ages. CD rates increased among women in all age groups from 1996 to 2009, according to birth data from the Centers for Disease Control and Prevention National Center for Health Statistics (CDC/ NCHS) (Fig. 4).3 Every age group had an increase of at least
50
1996
50%.3 Women aged 20-24 had the largest increase at 64%.3 In 1996 and 2009, the cesarean rate for mothers aged 40-54 years was more than twice the rate for mothers under age 20, illustrating that the cesarean rate increases with advancing maternal age.3 The CDC/NCHS birth data also show that all racial and ethnic groups experienced increases of at least 50% in CD rates from 1996 to 2009 (Fig. 5).6 In 2009, CD rates were highest among non-Hispanic black women (35%) and lowest among American Indian or Alaska Native women (28%).6 Preliminary data for 2010 show that the total CD rate for non-Hispanic black women was 35.5%, for non-Hispanic white women it was 32.6%, and for Hispanic women it was 31.8%.5 CD rates have also increased across gestational age. Rates are the highest at earlier gestational ages. Using 2009 CDC/ NCHS birth data, the CD rate was 54% for early preterm births (⬍34 weeks’ gestation), 42% for late preterm births (34-36 weeks’ gestation), and 31% for term births (⬎37
46.7
2009 40.6
40 34.4 30.3
30
30.2
27.4
26.1 22.6
22.3 19.6
20
16.7 13.9
10
0 Under 20
20–24
25–29
30–34
35–39
40–54
Source: Martin JA, Hamilton BE, Ventura SJ, et al. Births: Final data for 2009. National vital statistics reports; vol 60 no 1. Hyattsville, MD: National Center for Health Statistics. 2011.
Figure 4 CD rates, by age of mother: United States, 1996 and 2009.6,9 (Color version of figure is available online.)
Epidemiology of primary cesarean delivery
311
40
1996
35
2009 33
33
32
30
28 22
21 19
20
20 18
10
0 Non-Hispanic black
Non-Hispanic white
Asian or Pacific Islander
Hispanic
American Indian or Alaska Native
Sources: 1996 Data from Menacker F, Hamilton BE: Recent trends in cesarean delivery in the United States. NCHS Data Brief 35:1-8, 2010 2009 Data calculated from Center for Disease Control and Prevention. National Center for Health Statistics. VitalStats. National Vital Statistics System. http://www.cdc.gov/nchs/vitalstats.htm
Figure 5 CD rates, by race and Hispanic origin of mother: United States, 1996 and 2009.3,9 (Color version of figure is available online.)
weeks’ gestation).6 Between 1996 and 2006, the cesarean rate increased by 36% for early preterm deliveries and by almost 50% for late preterm and term deliveries.9 There is large variation in CD rates across the United States (Fig. 6).3 In 2009, total cesarean rates ranged from a low of ⬍25% in 4 states (Alaska, Idaho, New Mexico, and Utah) to a high of ⬎35% in 11 states (Alabama, Connecticut, Delaware, Florida, Kentucky, Louisiana, Mississippi, New Jersey, South Carolina, Texas, and West Virginia).3 Louisiana had the highest rate (39.6%).3 Every state and the District of Columbia experienced a significant rise between 1996 and 2009 (Fig. 7).3,9 Forty-three states and the District of Columbia had increases of at least 50%; 9 states had increases of 70% or more.3,9 Rhode Island had the largest increase (85%).3,9
International CD Trends The United States CD rate is relatively higher than that of other industrialized nations’. Among the 30 countries that provided data to the Organisation for Economic Co-operation and Development in 2008, CD rates ranged from a low of 14.3% for the Netherlands to a high of 43.9% for Mexico (Fig. 8).10 The total CD rate in the United States was higher than the rate for 24 of the other 29 countries.10 Compared with the United States cesarean rate, the Canadian rate was 18% lower, the rate for the United Kingdom was 28% lower, the French rate was 38% lower, and the Dutch rate was 56% lower.10 High rates of CD also affect Latin America. Taljaard and colleagues11 examined the CD rates for 120 institutions in 8 countries in Latin America. The overall CD rate was
Figure 6 Cesarean rate by state: United States, 2009.3 (Color version of figure is available online.)
A. Boyle and U.M. Reddy
312
Figure 7 Percent increase in cesarean rates by state: United States, 1996-2009.3,9 (Color version of figure is available online.)
35%, but the range among institutions was 0%-85%. Even after risk adjustment, CD rates ranged from 11% to 78%.11 The authors found that characteristics of institutions explained 48% of the variability among risk-adjusted rates.11 These characteristics included being a private as opposed to a public institution, having some economic incentive for CD as opposed to no incentive, and having ⬎50 maternity beds.11 Hanley et al12 also found marked variations in CD rates in British Columbia. Reviewing all deliveries from 2004 to 2007, they found that the rate of primary CD varied from
Netherlands Iceland Finland Denmark Sweden Slovenia Norway Israel Poland France Estonia Czech Republic New Zealand United Kingdom Spain Slovak Republic Ireland Canada Austria Germany Luxembourg Australia Hungary Switzerland United States Portugal Korea Turkey Italy Mexico
16.1% to 27.5%, whereas assisted vaginal delivery rates varied from 8.6% to 18.6%.12 After controlling for maternal characteristics and conditions known to increase the likelihood of CD and assisted vaginal delivery, rates still varied 2-fold.12 Adjusted CD rates ranged from 14.7% to 27.6%, and adjusted assisted vaginal delivery rates ranged from 6.5% to 15.3%.12 The authors found that there was substantial regional variation in the use of CD, which could not be explained by patient illness or preferences.12 They concluded that this variation likely reflected differences in practitioners’ approaches to medical decision-making.12
14.3 16.1 16.5 16.6 16.8 17.0 17.1 18.8 19.3 19.9 20.0 20.5 22.8 23.4 24.6 24.7 25.6 26.6 27.5 29.4 30.2 30.8 31.4 31.6 32.3 32.7 35.4 37.7 38.5 43.9
0.0
10.0
20.0
30.0
40.0
50.0
Source: Organisation for Economic Co-operation and Development. OECD Health Data 2011- Frequently Requested Data. http://www.oecd.org/document/16/0,3746,en_2649_33929_2085200_1_1_1_1,00.html
Figure 8 Percentage of cesarean births: Organisation for Economic Co-operation and Development countries, 2008.10 (Color version of figure is available online.)
Epidemiology of primary cesarean delivery In 2009, Brennan and colleagues13 examined 9 institutional cohorts, each from a different country. They classified each pregnancy using Robson’s14 10-group system based on characteristics of the pregnancy: single versus multiple gestation, nulliparity versus multiparity with or without a previous CD, spontaneous versus induced labor, earlier or later than 37 weeks’ gestation, and fetal presentation. They found that breech, multiple gestations, and preterm deliveries were a fairly constant proportion of each population and contributed relatively little to overall CD rates.13 Instead, overall CD rates correlated with CD rates in nulliparous women at term with a single fetus with cephalic presentation; CD in this population explained 98% of interinstitutional variation in overall CD rate.13 In this study, TSCN (term, singleton, cephalic, nulliparous) women contributed an average of 34% to overall CD rates.13 The authors pointed out that this is a low-risk cohort amenable to effective intrapartum corrective intervention.13 In a different study, Brennan et al15 compared the TSCN cesarean rate with the overall cesarean rate in a single large institution in Ireland over a 35-year period. They found that, between 1974 and 2008, the overall cesarean rate increased from 5% to 19.1% and the TSCN cesarean rate increased from 4.4% to 15.8%.15 TSCN inductions increased from 19.7% to 32.7%, and the intrapartum cesarean rate in TSCN inductions rose from 4.1% to 27.3%.15 Institutional CD rates correlated with TSCN cesarean rates throughout the 35-year period.15 The authors estimated that 97% of the variation in overall institutional CD rates for the 35 years could be explained by the TSCN CD rate.15
Reasons for Increased CD Rates Barber et al16 looked at indications for CD at a single academic hospital between 2003 and 2009. They found that the CD rate increased from 26% to 36.5% during this period, and that 50% of the increase was attributable to an increase in primary CD.16 The relative contributions of each indication to the total increase in primary cesarean rate were nonreassuring fetal status (32%), labor arrest disorders (18%), multiple gestation (16%), suspected macrosomia (10%), preeclampsia (10%), maternal request (8%), maternal-fetal conditions (5%), and other obstetrical conditions (1%).16 Like Brennan, Main et al17 found large variation in management of the TSCN delivery in their cohort study of 20 birthing units in California. Strong correlations were found between CD rates and labor induction rates as well as CD rates and early labor admission rates.17 The strongest correlation was found between TSCN CD rates and a combined measure of induction and early labor admission; 53% percent of the interhospital variation in CD rate could be explained by these 2 practices.17 They concluded that the TSCN cesarean rate was strongly influenced by these elective obstetrical practices.17 In a retrospective cohort study of CD among 7804 TSCN women at a single large institution, Ehrenthal et al18 found that labor induction was used in 43.6% of cases, 39.9% of which were elective. Use of labor induction was associated
313 with increased odds of CD, and the association remained significant after adjustment for maternal demographic characteristics, medical risk, and pregnancy complications (adjusted odds ratio 1.93, 1.71-2.2).18 The contribution of labor induction to CD in the TSCN cohort was approximately 20%.18 Among TSCN women undergoing labor induction, 40.7% underwent cervical ripening, indicating a Bishop Score of ⬍6; among TSCN women with an elective indication, 37% had an unfavorable cervix.18 Indications for CD were labor dystocia in 75.1% of cases, fetal distress in 28.2%, maternal medical indications in 1.6%, and “other” indications in 2.9%.18 The risk factors that contributed most to CD in this population were labor induction and maternal obesity before pregnancy.18 The Consortium on Safe Labor (CSL) collected labor and delivery information from 228,668 electronic medical records from 19 hospitals across the United States from 2002 to 2008.19 The overall CD rate was 30.5%, but rates among institutions ranged from 20% to 44%.19 Of women attempting vaginal delivery, 43.8% were induced.19 The CD rate for induced labor was roughly double that of spontaneous labor in all pregnancies (21.1% vs 11.8%) and in TSCN women (31.4% vs 14.2%).19 Half of CDs for dystocia in induced labor were performed before 6 cm of cervical dilation.19 Among intrapartum CDs, approximately half were performed for “failure to progress” or “cephalopelvic disproportion,” and more than a quarter were performed for indications of “nonreassuring fetal testing” or “fetal distress.”19 One-third of CDs at the second stage were performed at ⬍3 hours in nulliparous women, whereas a quarter were performed at ⬍2 hours in multiparous women.19 Using contemporary data, the CSL developed new labor curves based on 62,415 parturients with a singleton term gestation, spontaneous onset of labor, a vertex presentation, vaginal delivery, and a normal perinatal outcome.20 Based on the Friedman labor curves, which were designed ⬎50 years ago, active phase labor is typically believed to start at 4 cm dilation.21 Appropriate labor progression in the active phase has been defined as cervical dilation of at least 1.2 cm/h in nulliparous women and at least 1.5 cm/h in multiparous women.21 No change in cervical dilation in the presence of adequate uterine contractions for ⬎2 hours is typically considered labor arrest.22 However, the CSL labor curves showed that progress from 4 to 6 cm was far slower than previously described.20 In fact, the rate of cervical dilation accelerated after 6 cm dilation, suggesting that 6 cm should be considered the start of the active phase of labor.20 Allowing labor to continue for a longer period before 6 cm of cervical dilation may potentially reduce the rate of intrapartum CDs, which would have a substantial effect on the total CD rate.
Conclusions Since 1996, the total CD rate in the United States has increased significantly among women of all ages, races, gestational ages, and in every state. The increase in the total CD rate has been paralleled by an increase in the primary CD rate. Based on the data, several factors need to be addressed to
314 decrease the primary CD rate. First, improved diagnosis of clinically accepted indications for CD is needed because the leading indications—“failure to progress,” “cephalopelvic disproportion,” “nonreassuring fetal testing,” and “fetal distress”—are somewhat subjective. Second, a high rate of labor induction is associated with an increased CD rate in nulliparous women, so addressing elective inductions in nulliparous women may have a substantial impact on CD rates. Third, a substantial proportion of CDs for failure to progress may be avoided if practitioners wait for the active phase of labor to commence, which appears to be at 6 cm dilation. Hospital-level data show that the large variation in management of TSCN births contributes significantly to the increased total cesarean rate. Recognizing the role that TSCN CD plays in the overall CD rate, one of the objectives of the US Department of Health and Human Services’ Healthy People 2020 initiative is to reduce cesarean births among lowrisk (full-term, singleton, vertex presentation) women giving birth for the first time by 10%—from 26.5% in 2007 to 23.9% in 2020.23 Targeting the labor management of this particular subgroup of women has the potential to make a sizable impact on the overall cesarean rate in the United States.
References 1. Boley JP: The history of caesarean section. 1935. CMAJ 145:319-322, 1991 2. Hall MJ, DeFrances CJ, Williams SN, et al: National Hospital discharge survey: 2007 summary. Natl Vital Stat Rep 29:1-24, 2010 3. Martin JA, Hamilton BE, Ventura SJ, et al: Births: Final data for 2009. Natl Vital Stat Rep 60:1-35, 2011 4. MacDorman M, Declercq E, Menacker F: Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol 38:179-192, 2011 5. Hamilton BE, Martin JA, Ventura SJ: Births: Preliminary data for 2010. Natl Vital Stat Rep 60:1-14, 2011 6. Center for Disease Control and Prevention, National Center for Health Statistics: VitalStats. National Vital Statistics System. Available at: http://www.cdc.gov/nchs/vitalstats.htm. Accessed March 5, 2012 7. Center for Disease Control and Prevention, National Center for Health Statistics: User’s Guide to the 2007 Natality Public Use File. Available at: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/ DVS/natality/UserGuide2007.pdf. Accessed March 5, 2012
A. Boyle and U.M. Reddy 8. American College of Obstetricians and Gynecologists: ACOG Practice Bulletin no. 115: Vaginal birth after previous Cesarean delivery. Obstet Gynecol 116:450-463, 2010 9. Menacker F, Hamilton BE: Recent trends in cesarean delivery in the United States. NCHS Data Brief 35:1-8, 2010 10. Organisation for Economic Co-operation and Development: Health Data 2011—Frequently Requested Data. Available at: http://www. oecd.org/document/16/0,3746,en_2649_33929_2085200_1_1_1_1,00. html. Accessed February 28, 2012 11. Taljaard M, Donner A, Villar J, et al: Understanding the factors associated with differences in caesarean section rates at hospital level: The case of Latin America. Paediatr Perinat Epidemiol 23:574-581, 2009 12. Hanley GE, Janssen PA, Greyson D: Regional variation in the cesarean delivery and assisted vaginal delivery rates. Obstet Gynecol 115:12011208, 2010 13. Brennan DJ, Robson MS, Murphy M, et al: Comparative analysis of international cesarean delivery rates using 10-group classification identifies significant variation in spontaneous labor. Am J Obstet Gynecol 201:e1-e8, 2009 14. Robson M: Classification of caesarean sections. Fetal Matern Med Rev 12:23-39, 2001 15. Brennan DJ, Murphy M, Robson MS, et al: The singleton, cephalic, nulliparous woman after 36 weeks of gestation: Contribution to overall cesarean delivery rates. Obstet Gynecol 117:273-279, 2011 16. Barber EL, Lundsberg LS, Belanger K, et al: Indications contributing to the increasing cesarean delivery rate. Obstet Gynecol 118:29-38, 2011 17. Main EK, Moore D, Farrell B, et al: Is there a useful cesarean birth measure? Assessment of the nulliparous term singleton vertex cesarean birth rate as a tool for obstetric quality improvement. Am J Obstet Gynecol 194:1644-1651, 2006 18. Ehrenthal DB, Jiang X, Strobino DM: Labor induction and the risk of a cesarean delivery among nulliparous women at term. Obstet Gynecol 116:35-42, 2010 19. Zhang J, Troendle J, Reddy UM, et al: Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 203:e1-e10, 2010 20. Zhang J, Landy HJ, Branch DW, et al: Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116: 1281-1287, 2010 21. Kilpatrick S, Garrison E: Normal labor and delivery, in Gabbe SG, Niebyl JR, Simpson JL (eds): Obstetrics: Normal and Problem Pregnancies, 5th ed. Philadelphia, PA, Churchill Livingstone, 2007, p 314 22. Battista LR, Wing DA: Abnormal labor and induction of labor, in Gabbe SG, Niebyl JR, Simpson JL (eds): Obstetrics: Normal and Problem Pregnancies, 5th ed. Philadelphia, PA, Churchill Livingstone, 2007, p 325 23. US Department of Health and Human Services: 2020 Topics and Objectives, Maternal Infant and Child Health. Available at: http:// healthypeople.gov/2020/topicsobjectives2020/objectiveslist.aspx? topicId⫽26. Accessed March 4, 2012