- Email: [email protected]
Regional differences in operative obstetrics: a look to the South
Regional Differences in Operative Obstetrics: A Look to the South LEE A. LEARMAN, MD, PhD Objective: To compare operative delivery rates across regions of the United States from 1987 to 1994 and to evaluate how the rates of severe obstetric lacerations changed during the same period. Methods: I used diagnosis and procedure data from the National Hospital Discharge Survey and natality data from the National Center for Health Statistics to describe temporal and regional variations in the rates of cesarean, forceps, and vacuum delivery. I described temporal trends in the rates of cervical and severe perineal lacerations during the same period. I performed exploratory analyses of detailed 1990 data to test for regional differences in demographic risk factors that might explain differences in operative delivery rates. Results: Between 1987 and 1994, cesarean delivery rates fell from approximately 25% to less than 22% in all regions except the South. Operative vaginal delivery rates were stable at 10 –12% and were consistently lowest in the Northeast (8.2% in 1994) and highest in the South (12.9% in 1994). Vacuum surpassed forceps deliveries in all regions except the South. The rates of cervical and fourth-degree perineal lacerations declined by 57% and 40%, respectively, whereas the rate of third-degree lacerations did not decline. Demographic risk factors for cesarean delivery were no more prevalent in the South than in other regions. Age under 25 years was the only demographic risk factor for forceps delivery that was more prevalent in the South. Conclusion: In all but the southern United States, cesarean delivery rates declined and vacuum surpassed forceps delivery. These regional differences are not explained by differences in demographic risk factors. (Obstet Gynecol 1998;92: 514 –9. © 1998 by The American College of Obstetricians and Gynecologists.)
Nearly one in three deliveries in the United States occur with operative intervention,1 but the prevalence and type of interventions vary considerably across geographic regions. A 1987 report from the Centers for Disease Control2 noted the cesarean delivery rate to be
From the Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California.
514 0029-7844/98/$19.00 PII S0029-7844(98)00260-9
highest in the Northeast (26.3%), the forceps delivery rate highest in the South (12.1%), and the vacuum delivery rate highest in the West (3.7%). No study has evaluated whether the overall decline in the cesarean delivery rate during the last decade has occurred equally across the United States. It is unclear whether regional differences in operative obstetrics have widened, narrowed, or remained stable during this period. Although forceps delivery is still considered a safe and important technique in the United States, European proponents of vacuum extraction are finding more like-minded colleagues on this side of the Atlantic. In a review of eight acceptably controlled studies3 the Oxford-based Cochrane collaboration concluded that vacuum extraction reduces severe maternal injuries compared with forceps delivery and that there is no evidence of any compensating benefits to support the use of forceps. A recent survey of North American residency program directors4 reported that the vacuum was the preferred instrument for operative vaginal delivery in about one-third of obstetrics and gynecology training programs. A separate survey of ACOG fellows by the same authors5 found that preference for vacuum over forceps use increases with the recency of training. No published reports have quantified the transition from forceps to vacuum delivery in the obstetric population of the United States. Although one would expect a decline in severe obstetric trauma to follow from a switch to vacuum use, this hypothesis remains untested. Using databases compiled by the National Center for Health Statistics, I compared cesarean and operative vaginal delivery rates across four major regions of the country from 1987 to 1994. I calculated rates of cervical and severe perineal lacerations over the same time period and compared these to temporal trends in forceps use. I then conducted a set of exploratory analyses using detailed data from 1990 to evaluate whether differences in demographic risk factors could explain the regional differences in operative delivery.
Obstetrics & Gynecology
Materials and Methods This study used two databases created and maintained by the National Center for Health Statistics. The National Hospital Discharge Survey has been conducted annually since 1965 and is used to estimate acute-care hospital use in the United States. The National Hospital Discharge Survey has been used for decades to track the rates of obstetric diagnoses and procedures in the United States, including operative delivery,2 hypertensive diseases,6 and ectopic pregnancy.7 Each year the survey uses a national probability sample of more than 200,000 admissions to general and short-stay hospitals. The complex sampling scheme stratifies by geographic region and links the degree of sampling to the number of hospital beds. The National Hospital Discharge Survey record includes up to seven diagnoses and four procedures listed on each discharge abstract and encoded with the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM).8 Detailed National Hospital Discharge Survey diagnosis and procedure data for 1987–1994 are publicly available on diskettes for microcomputers that include software for querying the frequency of diagnoses or procedures, including regional distributions.9 The full survey dataset from 1990 is publicly available on a CD-ROM that includes a statistical export and tabulation system provided by the National Center for Health Statistics.10 This sophisticated software enables CD-ROM users to build record subsets defined by diagnosis, procedure, or demographic codes, create tables, and export data to other software systems for analysis. Population estimates are calculated by an intrinsic SUDAAN-based (Research Triangle Institute, Research Triangle Park, NC) estimation program.10 The National Hospital Discharge Survey is effective at sampling the many operative and spontaneous deliveries occurring in United States hospitals but underestimates spontaneous deliveries that occur at home or in free-standing birth centers. The National Center for Health Statistics uses natality statistics compiled from birth records to provide the most inclusive estimate of total deliveries in the United States. These are published as Vital Health Statistics of the United States,11 and are stratified by age, region, and race. To study temporal and regional trends in operative delivery, I defined the study population as all sampled women in the National Hospital Discharge Survey who underwent cesarean delivery (ICD-9-CM codes 74.0 – 74.29, 74.4, 74.99), forceps delivery (72.0 –72.4), and vacuum delivery (72.7) for each of the years from 1987 to 1994. I calculated rates of operative delivery per 100 live births in each geographic region using published natality statistics in the denominator and plotted these
VOL. 92, NO. 4, PART 1, OCTOBER 1998
Table 1. Regional Partitions of the National Center for Health Statistics Regions
States
Northeast Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania Midwest Michigan, Ohio, Illinois, Indiana, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas South Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Kentucky, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, Texas West Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, Washington, Oregon, California, Hawaii, Alaska.
over time. I used statistical software publicly available from the Centers for Disease Control and Prevention to calculate risk ratios and 95% confidence intervals (CIs) for cesarean, forceps, and vacuum delivery in the final year, 1994, according to geographic region. United States regions were those defined by the National Center for Health Statistics, which uses the partitions of the US Bureau of the Census (Table 1).12 To study temporal trends in severe obstetric lacerations, I defined the study population as all sampled women in the National Hospital Discharge Survey diagnosed with a cervical laceration (ICD-9-CM code 665.3), third-degree perineal laceration (664.3), or fourth-degree perineal laceration (664.4). I calculated rates of these obstetric lacerations per 100 live births using natality statistics in the denominator and plotted these over time. To explore the potential explanations for regional differences in the use of obstetric interventions, I performed a detailed analysis of 1990 National Hospital Discharge Survey data. I calculated risk ratios with 95% CIs to identify statistically significant risk factors for cesarean and operative vaginal delivery. I then compared the frequency of these risk factors between regions using x2 analyses. A probability level of P , .05 was set to determine statistical significance. In all analyses I followed the National Center for Health Statistics guidelines for presenting only estimates based on adequate sample sizes and relative standard errors of less than 30%. I determined whether the threshold of 30% was exceeded using tables and formulae published in the National Hospital Discharge Survey documentation incorporating first-order Taylor approximations of the deviation of estimates from their expected values.12 With many hundreds of thousands of patients in each subgroup compared, this study had sufficient power (more than 99%) to detect a difference
Learman
Regional Differences in Obstetrics 515
Figure 1. Rates of cesarean and operative vaginal delivery in the United States, 1987–1994: Rates per 100 live births of cesarean delivery (circle), total operative vaginal delivery (square), forceps delivery (cross), and vacuum delivery (triangle). All data points have a relative standard error of less than 5%.
in the rates of operative delivery of less than one per 100 live births with 95% confidence.13
Results Between 1987 and 1994, the cesarean delivery rate in the United States declined from 25% to 22%, and the operative vaginal delivery rate remained stable at 10 – 12%. Forceps use declined each year and vacuum surpassed forceps delivery in 1992 (Figure 1). Between 1987 and 1994, the rate of cervical lacerations declined by 57% from 0.5 to 0.2 per 100 live births (Relative risk [RR] 0.43, 95% CI 0.42, 0.44). The rate of fourth-degree perineal lacerations declined by 39% from 2.6 to 1.6 per 100 live births (RR 0.61, CI 0.60, 0.61). The rate of third-degree lacerations showed no consistent pattern (Figure 2). Regional differences in operative delivery rates over time are striking. In 1987, the cesarean delivery rate was around 25% in all regions. By 1994, the cesarean delivery rate fell to less than 20% in all regions except the South, where it remained above 25% (Figure 3). In 1987, there were large regional differences in operative vaginal delivery rates. In the South nearly one in six deliveries involved the use of forceps or vacuum, as compared with rates of 8 –11% in other regions (Figure 4). Over the next 8 years, each region showed a marked decline in forceps use from its 1987 baseline. Vacuum surpassed forceps delivery first in the West (1988) and then in the Northeast (1990), and the gap continued to widen through 1994 in both regions. In the Midwest, vacuum surpassed forceps in 1991, and the gap began to stabilize by 1994. The South was the only region in which forceps continued to be the most popular method
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Figure 2. Rates of severe obstetric lacerations in the United States, 1987–1994: Rates per 100 live births of third-degree perineal (triangle), fourth-degree perineal (diamond), and cervical (circle) lacerations. All data points have a relative standard error of less than 5%.
of operative vaginal delivery. The forceps delivery rate in the South declined from 1987 to 1991, then plateaued between 7 and 8% of live births (Figure 4). I could not evaluate regional differences in the rates of severe obstetric lacerations because the number of cases was too low in some regions to produce a reliable estimate according to standards of the National Center for Health Statistics. By 1994, substantial regional differences were evident in the rates of cesarean, vacuum, and forceps delivery (Table 2). The cesarean rate in the South (25.2%) was more than one-third higher than in the remainder of the
Figure 3. Regional differences in cesarean delivery: Cesarean delivery rates per 100 live births in the South (triangles), Midwest (circles), Northeast (diamonds), and West (squares). All data points have a relative standard error of less than 5%.
Obstetrics & Gynecology
Figure 4. Regional differences in operative vaginal delivery: Operative delivery rates per 100 live births in the West (top left panel), Northeast, (top right panel), Midwest (bottom left panel), and South (bottom right panel). Solid symbols represent the rates of total operative vaginal delivery, open squares represent forceps delivery, and open triangles represent vacuum delivery. All data points have a relative standard error of less than 5%.
United States. Southern gravidas were more than three times as likely to be delivered with forceps (7.5%) than their counterparts in the Northeast and West. In the Table 2. Operative Delivery Rates in the United States by Geographic Region, 1994 Operative delivery rates Mode by region Cesarean delivery South Midwest Northeast West Vacuum delivery South Midwest Northeast West Forceps delivery South Midwest Northeast West
Rate*
Rate ratio
95% CI
25.2 19.6 19.4 18.5
1.36 1.06 1.05 1.0
1.36, 1.37 1.05, 1.06 1.04, 1.05 Referent
5.4 6.2 5.9 9.8
1.0 1.14 1.08 1.81
Referent 1.13, 1.15 1.07, 1.09 1.79, 1.83
7.5 3.4 2.3 2.4
3.22 1.46 1.0 1.03
3.17, 3.28 1.43, 1.48 Referent 1.01, 1.05
CI 5 confidence interval. * Rates per 100 live births.
VOL. 92, NO. 4, PART 1, OCTOBER 1998
West, the cesarean delivery rate (18.5%) was the lowest in the United States, but nearly one in ten deliveries (9.8%) was performed by vacuum extraction. Exploratory analyses of deliveries in 1990 revealed a higher rate of cesarean delivery among women in older age groups. Compared with gravidas age 15–24 years, those age 25–34 years were approximately 30% more likely to undergo cesarean delivery (RR 1.29, 95% CI 1.29, 1.30) and gravidas age 35– 44 years were more than 60% more likely to be delivered by cesarean (RR 1.62, 95% CI 1.61, 1.63). The associations of race and health insurance with cesarean delivery were statistically significant but small in magnitude. The risk of being delivered by cesarean was slightly higher among black gravidas (RR 1.04, 95% CI 1.03, 1.05) and among gravidas with private health insurance (RR 1.05, 95% CI 1.05, 1.05). Gravidas at increased risk for forceps delivery were under 35, white, and privately insured. Compared with women age 35– 44, younger gravidas were approximately 20% more likely to have a forceps delivery (RR 1.19, 95% CI 1.17, 1.21 for age 15–24 years; RR 1.23, 95% CI 1.21, 1.24 for age 25–34 years). White gravidas were at nearly twice the risk of having a forceps delivery (RR 1.92, 95% CI 1.89, 1.95), and the risk for privately insured gravidas was more than 50% higher than for publicly insured women (RR 1.52, 95% CI 1.51, 1.54). A similar pattern emerged for vacuum delivery, which was more common among white gravidas and younger gravidas but was unrelated to insurance source. As compared with women age 35– 44 years, those age 25–34 years were at increased risk of having a vacuum delivery (RR 1.23, 95% CI 1.20, 1.25). Gravidas age 15–24 years had more than a one-third increased risk of having a vacuum delivery (RR 1.36, 95% CI 1.34, 1.39). White gravidas were more likely to have a vacuum delivery (RR 1.18, 95% CI 1.16, 1.20), and insurance source was unrelated to vacuum delivery rates (RR 1.01, 95% CI 1.00, 1.02). Demographic risk factors for operative delivery were no more prevalent in the regions with higher rates of obstetric interventions than in other regions (Figure 5). Although the rates of cesarean and forceps delivery were greatest in the South, the proportion of gravidas who were white or privately insured fell between the rates for gravidas in the Northeast and Midwest. Although advanced maternal age was a risk factor for cesarean delivery, a lower proportion of Southern parturients were age 35– 44 years than in the remainder of the United States (RR 0.81, 95% CI 0.80, 0.81). The South did have a higher proportion of gravidas under the age of 25 years than did regions with lower rates of forceps delivery (RR 1.24, 95% CI 1.24, 1.24). Although vacuum delivery was more common in the West than in any
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Regional Differences in Obstetrics 517
Figure 5. Regional differences in demographic risk factors for operative delivery: Rates of demographic risk factors per 100 live births in the West (open bars), Northeast (vertical striped bars), Midwest (diagonal striped bars), and South (solid bars). All rate differences are statistically significant by x2 analysis, P , .001.
other region, the West ranked third in the proportion of gravidas under 25 years old and ranked last in the proportion of deliveries occurring to white women.
Discussion The cesarean delivery rate declined substantially in the United States after 1987, and by 1994 was lower than 20% in all regions except the South, where the rate was sustained above 25%. The identification of regional differences can bring focus to national strategies to reduce the cesarean delivery rate toward the 15% goal described in Healthy People 2000.14 A detailed look at the indications for primary cesarean delivery and rates of vaginal birth after cesarean would help determine whether the South deviates from other regions in one or both of these areas. Vacuum extraction became the preferred operative vaginal delivery method in all regions except the South, where the forceps delivery rate declined initially after 1987 and then stabilized at approximately 60% of vaginal operations. It is important to note that this study could not measure directly the transition from forceps to vacuum procedures in a group of obstetricians over time. Rather, the study provides indirect evidence based on population shifts in the relative use of these procedures. I could not use the National Hospital Discharge Survey database to study relationships of operative delivery methods with neonatal morbidity because these were recorded too infrequently in the discharge abstracts of neonates to produce a reliable estimate. As the number of forceps deliveries available for training declines, residency programs in obstetrics and gynecology will be challenged to produce graduates who are skilled in these procedures. In 20 years, will the
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South be the last bastion of training in forceps delivery? If the regional differences in 1994 continue to widen, forceps training could disappear in western, northeastern and midwestern programs long before its demise in the southern United States. As forceps deliveries declined from 1987 to 1994, so did the rates of fourth-degree perineal and cervical lacerations. The rate of third-degree perineal lacerations did not decline. This temporal association does not provide definitive evidence of a causal link between forceps use and maternal morbidity. The decline in cervical laceration rates could be explained by the alternative hypothesis that over time there were more deliveries of nulliparas, or differences in the use of oxytocin and cervical ripening agents. The decrease in fourth-degree perineal lacerations could be explained by the alternative hypothesis that routine episiotomy use declined during the same period. A decline in episiotomy use has been associated with fewer fourthdegree perineal lacerations.15,16 Exploratory analyses of data from 1990 showed that demographic risk factors for cesarean delivery were not more prevalent in the South than in regions with lower rates of these operations. Operative delivery was more common among gravidas who were white, privately insured, or at the extremes of age (more cesarean deliveries if older, more operative vaginal deliveries if younger). These findings are consistent with demographic trends demonstrated in the United States from 1980 to 19872 and a more recent prospective study finding advanced maternal age to be an independent predictor of cesarean delivery.17 Risk factors for cesarean delivery and most risk factors for forceps delivery were no more prevalent in the South than in regions with lower intervention rates. Regional differences exist in the rates of other surgical procedures in women, including hysterectomy, tubal sterilization, and treatments for localized breast cancer and ductal carcinoma in-situ.18 –21 These differences are not explained by the frequency or severity of underlying indications for intervention. Further research should focus on potential reasons for regional differences in obstetric practice. There may be differences in important clinical risk factors for operative delivery beyond the basic demographic ones I examined. Clinical decisions may be made differently in the southern United States than they are elsewhere. Important regional differences may exist in the professional and practice characteristics of obstetricians, including recency of training, postgraduate education activities, and the medicolegal environment.22 Differences might also exist in the preferences of patients or in their degree of involvement in decision making. These differences cannot be studied using national databases, but rather by
Obstetrics & Gynecology
surveying a representative sample of obstetricians and patients in selected communities across the United States and assessing their practice patterns, attitudes, preferences, and support for collaborative decision making.
References 1. National Center for Health Statistics. Report of final natality statistics, 1995. Monthly Vital Statistics Report Vol. 45(11). Washington, DC: United States Department of Health and Human Services, 1997. 2. Zahniser SC, Kendrick JS, Franks AL, Saftlas AF. Trends in obstetric operative procedures, 1980 to 1987. Am J Public Health 1992;82:1340 – 4. 3. Johanson RB. Vacuum extraction vs. forceps delivery. In: Enkin MW, Keirse MJNC, Renfrew MJ, Neilson JP, eds. Pregnancy and childbirth module. Cochrane database of systematic reviews: Review no. 03256, 10 1994 Mar 10. Published through Cochrane Updates on Disk. Oxford, UK: Update Software, 1994, Disk Issue 1. 4. Bofill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Forceps and vacuum delivery: A survey of North American residency programs. Obstet Gynecol 1996;88:622–5. 5. Bofill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Operative vaginal delivery: A survey of fellows of ACOG. Obstet Gynecol 1996;88:1007–10. 6. Saftlas AF, Olson DR, Franks AL, Atrash HK, Pokras R. Epidemiology of preeclampsia and eclampsia in the United States, 1979 – 1986. Am J Obstet Gynecol 1990;163:460 –5. 7. Goldner RE, Lawson HW, Xia Z, Atrash HK. Surveillance for ectopic pregnancy–-United States 1970 –1989. In: CDC surveillance summaries (December). MMWR Morbid Mortal Wkly Rep 1993; 42(SS-6):73– 85. 8. 1995 International Classification of Diseases, 9th Revision Clinical Modification. DHHS publication PHS 91-1260. Washington, DC: United States Department of Health and Human Services, 1991. 9. National Center for Health Statistics. National Hospital Discharge Survey data access system, advanced version, detailed diagnoses and procedures, 1987–1994.Publications PB93-504702, PB93504728, PB93-504744, PB93-504819, PB93-505857, PB94-504537, PB95-503512, PB96-502687. Springfield, VA: National Technical Information Service, 1993–1996. 10. National Center for Health Statistics. 1990 National Hospital Discharge Survey CD-ROM series 13, no. 1. Washington, DC: United States Government Printing Office, 1994. 11. National Center for Health Statistics. Vital health statistics of the United States, Volume I, natality, 1987–1994. Washington, DC: Public Health Service, 1989 –1996. 12. National Center for Health Statistics. 1990 National Hospital
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13. 14.
15.
16.
17. 18. 19.
20.
21.
22.
Discharge Survey public use data tape documentation. Hyattsville, MD: National Center for Health Statistics, 1992. Fleiss JL. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley and Sons, 1981;38 – 45. US Department of Health and Human Services. Healthy people 2000: National health promotion and disease prevention objectives. DHHS publication PHS 91-50212. Washington, DC: US Public Health Service, 1990. Ecker JL, Tan WM, Bansal RK, Bishop JT, Kilpatrick SJ. Is there a benefit to episiotomy at operative vaginal delivery? Observations over ten years in a stable population. Am J Obstet Gynecol 1997;176:411– 4. Helwig JT, Thorp JM, Bowes WA. Does midline episiotomy increase the risk of third- and fourth-degree lacerations in operative vaginal deliveries? Obstet Gynecol 1993;82:276 –9. Peipert JE, Bracken MB. Maternal age: An independent risk factor for cesarean delivery. Obstet Gynecol 1993;81:200 –5. Easterday CL, Grimes DA, Riggs JA. Hysterectomy in the United States. Obstet Gynecol 1983;62:203–12. Layde PM, Fleming D, Greenspan JR, Smith JC, Ory HW. Demographic trends of tubal sterilization in the United States, 1970 –75. Am J Public Health 1980;70:808 –12. Farrow DC, Hunt WC, Samet JM. Geographic variation in the treatment of localized breast cancer. N Engl J Med 1992;326:1097– 101. Ernster VL, Barclay J, Kerlikowske K, Grady D, Henderson C. Incidence of and treatment for ductal carcinoma in situ of the breast. JAMA 1996;275:913– 8. Localio AR, Lawthers AG, Bengston JM, Hebert LE, Weaver SL et al. Relationship between malpractice claims and cesarean delivery. JAMA 1993;269:366 –73.
Address reprint requests to:
Lee A. Learman, MD, PhD Department of Obstetrics and Gynecology–-Room 6D-14 San Francisco General Hospital 1001 Potrero Street San Francisco, CA 94110 E-mail: [email protected]
Received February 17, 1998. Received in revised form May 6, 1998. Accepted May 15, 1998. Copyright © 1998 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
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Regional Differences in Obstetrics 519
Nearly one in three deliveries in the United States occur with operative intervention,1 but the prevalence and type of interventions vary considerably across geographic regions. A 1987 report from the Centers for Disease Control2 noted the cesarean delivery rate to be
From the Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California.
514 0029-7844/98/$19.00 PII S0029-7844(98)00260-9
highest in the Northeast (26.3%), the forceps delivery rate highest in the South (12.1%), and the vacuum delivery rate highest in the West (3.7%). No study has evaluated whether the overall decline in the cesarean delivery rate during the last decade has occurred equally across the United States. It is unclear whether regional differences in operative obstetrics have widened, narrowed, or remained stable during this period. Although forceps delivery is still considered a safe and important technique in the United States, European proponents of vacuum extraction are finding more like-minded colleagues on this side of the Atlantic. In a review of eight acceptably controlled studies3 the Oxford-based Cochrane collaboration concluded that vacuum extraction reduces severe maternal injuries compared with forceps delivery and that there is no evidence of any compensating benefits to support the use of forceps. A recent survey of North American residency program directors4 reported that the vacuum was the preferred instrument for operative vaginal delivery in about one-third of obstetrics and gynecology training programs. A separate survey of ACOG fellows by the same authors5 found that preference for vacuum over forceps use increases with the recency of training. No published reports have quantified the transition from forceps to vacuum delivery in the obstetric population of the United States. Although one would expect a decline in severe obstetric trauma to follow from a switch to vacuum use, this hypothesis remains untested. Using databases compiled by the National Center for Health Statistics, I compared cesarean and operative vaginal delivery rates across four major regions of the country from 1987 to 1994. I calculated rates of cervical and severe perineal lacerations over the same time period and compared these to temporal trends in forceps use. I then conducted a set of exploratory analyses using detailed data from 1990 to evaluate whether differences in demographic risk factors could explain the regional differences in operative delivery.
Obstetrics & Gynecology
Materials and Methods This study used two databases created and maintained by the National Center for Health Statistics. The National Hospital Discharge Survey has been conducted annually since 1965 and is used to estimate acute-care hospital use in the United States. The National Hospital Discharge Survey has been used for decades to track the rates of obstetric diagnoses and procedures in the United States, including operative delivery,2 hypertensive diseases,6 and ectopic pregnancy.7 Each year the survey uses a national probability sample of more than 200,000 admissions to general and short-stay hospitals. The complex sampling scheme stratifies by geographic region and links the degree of sampling to the number of hospital beds. The National Hospital Discharge Survey record includes up to seven diagnoses and four procedures listed on each discharge abstract and encoded with the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM).8 Detailed National Hospital Discharge Survey diagnosis and procedure data for 1987–1994 are publicly available on diskettes for microcomputers that include software for querying the frequency of diagnoses or procedures, including regional distributions.9 The full survey dataset from 1990 is publicly available on a CD-ROM that includes a statistical export and tabulation system provided by the National Center for Health Statistics.10 This sophisticated software enables CD-ROM users to build record subsets defined by diagnosis, procedure, or demographic codes, create tables, and export data to other software systems for analysis. Population estimates are calculated by an intrinsic SUDAAN-based (Research Triangle Institute, Research Triangle Park, NC) estimation program.10 The National Hospital Discharge Survey is effective at sampling the many operative and spontaneous deliveries occurring in United States hospitals but underestimates spontaneous deliveries that occur at home or in free-standing birth centers. The National Center for Health Statistics uses natality statistics compiled from birth records to provide the most inclusive estimate of total deliveries in the United States. These are published as Vital Health Statistics of the United States,11 and are stratified by age, region, and race. To study temporal and regional trends in operative delivery, I defined the study population as all sampled women in the National Hospital Discharge Survey who underwent cesarean delivery (ICD-9-CM codes 74.0 – 74.29, 74.4, 74.99), forceps delivery (72.0 –72.4), and vacuum delivery (72.7) for each of the years from 1987 to 1994. I calculated rates of operative delivery per 100 live births in each geographic region using published natality statistics in the denominator and plotted these
VOL. 92, NO. 4, PART 1, OCTOBER 1998
Table 1. Regional Partitions of the National Center for Health Statistics Regions
States
Northeast Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania Midwest Michigan, Ohio, Illinois, Indiana, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas South Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Kentucky, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, Texas West Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, Washington, Oregon, California, Hawaii, Alaska.
over time. I used statistical software publicly available from the Centers for Disease Control and Prevention to calculate risk ratios and 95% confidence intervals (CIs) for cesarean, forceps, and vacuum delivery in the final year, 1994, according to geographic region. United States regions were those defined by the National Center for Health Statistics, which uses the partitions of the US Bureau of the Census (Table 1).12 To study temporal trends in severe obstetric lacerations, I defined the study population as all sampled women in the National Hospital Discharge Survey diagnosed with a cervical laceration (ICD-9-CM code 665.3), third-degree perineal laceration (664.3), or fourth-degree perineal laceration (664.4). I calculated rates of these obstetric lacerations per 100 live births using natality statistics in the denominator and plotted these over time. To explore the potential explanations for regional differences in the use of obstetric interventions, I performed a detailed analysis of 1990 National Hospital Discharge Survey data. I calculated risk ratios with 95% CIs to identify statistically significant risk factors for cesarean and operative vaginal delivery. I then compared the frequency of these risk factors between regions using x2 analyses. A probability level of P , .05 was set to determine statistical significance. In all analyses I followed the National Center for Health Statistics guidelines for presenting only estimates based on adequate sample sizes and relative standard errors of less than 30%. I determined whether the threshold of 30% was exceeded using tables and formulae published in the National Hospital Discharge Survey documentation incorporating first-order Taylor approximations of the deviation of estimates from their expected values.12 With many hundreds of thousands of patients in each subgroup compared, this study had sufficient power (more than 99%) to detect a difference
Learman
Regional Differences in Obstetrics 515
Figure 1. Rates of cesarean and operative vaginal delivery in the United States, 1987–1994: Rates per 100 live births of cesarean delivery (circle), total operative vaginal delivery (square), forceps delivery (cross), and vacuum delivery (triangle). All data points have a relative standard error of less than 5%.
in the rates of operative delivery of less than one per 100 live births with 95% confidence.13
Results Between 1987 and 1994, the cesarean delivery rate in the United States declined from 25% to 22%, and the operative vaginal delivery rate remained stable at 10 – 12%. Forceps use declined each year and vacuum surpassed forceps delivery in 1992 (Figure 1). Between 1987 and 1994, the rate of cervical lacerations declined by 57% from 0.5 to 0.2 per 100 live births (Relative risk [RR] 0.43, 95% CI 0.42, 0.44). The rate of fourth-degree perineal lacerations declined by 39% from 2.6 to 1.6 per 100 live births (RR 0.61, CI 0.60, 0.61). The rate of third-degree lacerations showed no consistent pattern (Figure 2). Regional differences in operative delivery rates over time are striking. In 1987, the cesarean delivery rate was around 25% in all regions. By 1994, the cesarean delivery rate fell to less than 20% in all regions except the South, where it remained above 25% (Figure 3). In 1987, there were large regional differences in operative vaginal delivery rates. In the South nearly one in six deliveries involved the use of forceps or vacuum, as compared with rates of 8 –11% in other regions (Figure 4). Over the next 8 years, each region showed a marked decline in forceps use from its 1987 baseline. Vacuum surpassed forceps delivery first in the West (1988) and then in the Northeast (1990), and the gap continued to widen through 1994 in both regions. In the Midwest, vacuum surpassed forceps in 1991, and the gap began to stabilize by 1994. The South was the only region in which forceps continued to be the most popular method
516 Learman
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Figure 2. Rates of severe obstetric lacerations in the United States, 1987–1994: Rates per 100 live births of third-degree perineal (triangle), fourth-degree perineal (diamond), and cervical (circle) lacerations. All data points have a relative standard error of less than 5%.
of operative vaginal delivery. The forceps delivery rate in the South declined from 1987 to 1991, then plateaued between 7 and 8% of live births (Figure 4). I could not evaluate regional differences in the rates of severe obstetric lacerations because the number of cases was too low in some regions to produce a reliable estimate according to standards of the National Center for Health Statistics. By 1994, substantial regional differences were evident in the rates of cesarean, vacuum, and forceps delivery (Table 2). The cesarean rate in the South (25.2%) was more than one-third higher than in the remainder of the
Figure 3. Regional differences in cesarean delivery: Cesarean delivery rates per 100 live births in the South (triangles), Midwest (circles), Northeast (diamonds), and West (squares). All data points have a relative standard error of less than 5%.
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Figure 4. Regional differences in operative vaginal delivery: Operative delivery rates per 100 live births in the West (top left panel), Northeast, (top right panel), Midwest (bottom left panel), and South (bottom right panel). Solid symbols represent the rates of total operative vaginal delivery, open squares represent forceps delivery, and open triangles represent vacuum delivery. All data points have a relative standard error of less than 5%.
United States. Southern gravidas were more than three times as likely to be delivered with forceps (7.5%) than their counterparts in the Northeast and West. In the Table 2. Operative Delivery Rates in the United States by Geographic Region, 1994 Operative delivery rates Mode by region Cesarean delivery South Midwest Northeast West Vacuum delivery South Midwest Northeast West Forceps delivery South Midwest Northeast West
Rate*
Rate ratio
95% CI
25.2 19.6 19.4 18.5
1.36 1.06 1.05 1.0
1.36, 1.37 1.05, 1.06 1.04, 1.05 Referent
5.4 6.2 5.9 9.8
1.0 1.14 1.08 1.81
Referent 1.13, 1.15 1.07, 1.09 1.79, 1.83
7.5 3.4 2.3 2.4
3.22 1.46 1.0 1.03
3.17, 3.28 1.43, 1.48 Referent 1.01, 1.05
CI 5 confidence interval. * Rates per 100 live births.
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West, the cesarean delivery rate (18.5%) was the lowest in the United States, but nearly one in ten deliveries (9.8%) was performed by vacuum extraction. Exploratory analyses of deliveries in 1990 revealed a higher rate of cesarean delivery among women in older age groups. Compared with gravidas age 15–24 years, those age 25–34 years were approximately 30% more likely to undergo cesarean delivery (RR 1.29, 95% CI 1.29, 1.30) and gravidas age 35– 44 years were more than 60% more likely to be delivered by cesarean (RR 1.62, 95% CI 1.61, 1.63). The associations of race and health insurance with cesarean delivery were statistically significant but small in magnitude. The risk of being delivered by cesarean was slightly higher among black gravidas (RR 1.04, 95% CI 1.03, 1.05) and among gravidas with private health insurance (RR 1.05, 95% CI 1.05, 1.05). Gravidas at increased risk for forceps delivery were under 35, white, and privately insured. Compared with women age 35– 44, younger gravidas were approximately 20% more likely to have a forceps delivery (RR 1.19, 95% CI 1.17, 1.21 for age 15–24 years; RR 1.23, 95% CI 1.21, 1.24 for age 25–34 years). White gravidas were at nearly twice the risk of having a forceps delivery (RR 1.92, 95% CI 1.89, 1.95), and the risk for privately insured gravidas was more than 50% higher than for publicly insured women (RR 1.52, 95% CI 1.51, 1.54). A similar pattern emerged for vacuum delivery, which was more common among white gravidas and younger gravidas but was unrelated to insurance source. As compared with women age 35– 44 years, those age 25–34 years were at increased risk of having a vacuum delivery (RR 1.23, 95% CI 1.20, 1.25). Gravidas age 15–24 years had more than a one-third increased risk of having a vacuum delivery (RR 1.36, 95% CI 1.34, 1.39). White gravidas were more likely to have a vacuum delivery (RR 1.18, 95% CI 1.16, 1.20), and insurance source was unrelated to vacuum delivery rates (RR 1.01, 95% CI 1.00, 1.02). Demographic risk factors for operative delivery were no more prevalent in the regions with higher rates of obstetric interventions than in other regions (Figure 5). Although the rates of cesarean and forceps delivery were greatest in the South, the proportion of gravidas who were white or privately insured fell between the rates for gravidas in the Northeast and Midwest. Although advanced maternal age was a risk factor for cesarean delivery, a lower proportion of Southern parturients were age 35– 44 years than in the remainder of the United States (RR 0.81, 95% CI 0.80, 0.81). The South did have a higher proportion of gravidas under the age of 25 years than did regions with lower rates of forceps delivery (RR 1.24, 95% CI 1.24, 1.24). Although vacuum delivery was more common in the West than in any
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Figure 5. Regional differences in demographic risk factors for operative delivery: Rates of demographic risk factors per 100 live births in the West (open bars), Northeast (vertical striped bars), Midwest (diagonal striped bars), and South (solid bars). All rate differences are statistically significant by x2 analysis, P , .001.
other region, the West ranked third in the proportion of gravidas under 25 years old and ranked last in the proportion of deliveries occurring to white women.
Discussion The cesarean delivery rate declined substantially in the United States after 1987, and by 1994 was lower than 20% in all regions except the South, where the rate was sustained above 25%. The identification of regional differences can bring focus to national strategies to reduce the cesarean delivery rate toward the 15% goal described in Healthy People 2000.14 A detailed look at the indications for primary cesarean delivery and rates of vaginal birth after cesarean would help determine whether the South deviates from other regions in one or both of these areas. Vacuum extraction became the preferred operative vaginal delivery method in all regions except the South, where the forceps delivery rate declined initially after 1987 and then stabilized at approximately 60% of vaginal operations. It is important to note that this study could not measure directly the transition from forceps to vacuum procedures in a group of obstetricians over time. Rather, the study provides indirect evidence based on population shifts in the relative use of these procedures. I could not use the National Hospital Discharge Survey database to study relationships of operative delivery methods with neonatal morbidity because these were recorded too infrequently in the discharge abstracts of neonates to produce a reliable estimate. As the number of forceps deliveries available for training declines, residency programs in obstetrics and gynecology will be challenged to produce graduates who are skilled in these procedures. In 20 years, will the
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South be the last bastion of training in forceps delivery? If the regional differences in 1994 continue to widen, forceps training could disappear in western, northeastern and midwestern programs long before its demise in the southern United States. As forceps deliveries declined from 1987 to 1994, so did the rates of fourth-degree perineal and cervical lacerations. The rate of third-degree perineal lacerations did not decline. This temporal association does not provide definitive evidence of a causal link between forceps use and maternal morbidity. The decline in cervical laceration rates could be explained by the alternative hypothesis that over time there were more deliveries of nulliparas, or differences in the use of oxytocin and cervical ripening agents. The decrease in fourth-degree perineal lacerations could be explained by the alternative hypothesis that routine episiotomy use declined during the same period. A decline in episiotomy use has been associated with fewer fourthdegree perineal lacerations.15,16 Exploratory analyses of data from 1990 showed that demographic risk factors for cesarean delivery were not more prevalent in the South than in regions with lower rates of these operations. Operative delivery was more common among gravidas who were white, privately insured, or at the extremes of age (more cesarean deliveries if older, more operative vaginal deliveries if younger). These findings are consistent with demographic trends demonstrated in the United States from 1980 to 19872 and a more recent prospective study finding advanced maternal age to be an independent predictor of cesarean delivery.17 Risk factors for cesarean delivery and most risk factors for forceps delivery were no more prevalent in the South than in regions with lower intervention rates. Regional differences exist in the rates of other surgical procedures in women, including hysterectomy, tubal sterilization, and treatments for localized breast cancer and ductal carcinoma in-situ.18 –21 These differences are not explained by the frequency or severity of underlying indications for intervention. Further research should focus on potential reasons for regional differences in obstetric practice. There may be differences in important clinical risk factors for operative delivery beyond the basic demographic ones I examined. Clinical decisions may be made differently in the southern United States than they are elsewhere. Important regional differences may exist in the professional and practice characteristics of obstetricians, including recency of training, postgraduate education activities, and the medicolegal environment.22 Differences might also exist in the preferences of patients or in their degree of involvement in decision making. These differences cannot be studied using national databases, but rather by
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surveying a representative sample of obstetricians and patients in selected communities across the United States and assessing their practice patterns, attitudes, preferences, and support for collaborative decision making.
References 1. National Center for Health Statistics. Report of final natality statistics, 1995. Monthly Vital Statistics Report Vol. 45(11). Washington, DC: United States Department of Health and Human Services, 1997. 2. Zahniser SC, Kendrick JS, Franks AL, Saftlas AF. Trends in obstetric operative procedures, 1980 to 1987. Am J Public Health 1992;82:1340 – 4. 3. Johanson RB. Vacuum extraction vs. forceps delivery. In: Enkin MW, Keirse MJNC, Renfrew MJ, Neilson JP, eds. Pregnancy and childbirth module. Cochrane database of systematic reviews: Review no. 03256, 10 1994 Mar 10. Published through Cochrane Updates on Disk. Oxford, UK: Update Software, 1994, Disk Issue 1. 4. Bofill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Forceps and vacuum delivery: A survey of North American residency programs. Obstet Gynecol 1996;88:622–5. 5. Bofill JA, Rust OA, Perry KG, Roberts WE, Martin RW, Morrison JC. Operative vaginal delivery: A survey of fellows of ACOG. Obstet Gynecol 1996;88:1007–10. 6. Saftlas AF, Olson DR, Franks AL, Atrash HK, Pokras R. Epidemiology of preeclampsia and eclampsia in the United States, 1979 – 1986. Am J Obstet Gynecol 1990;163:460 –5. 7. Goldner RE, Lawson HW, Xia Z, Atrash HK. Surveillance for ectopic pregnancy–-United States 1970 –1989. In: CDC surveillance summaries (December). MMWR Morbid Mortal Wkly Rep 1993; 42(SS-6):73– 85. 8. 1995 International Classification of Diseases, 9th Revision Clinical Modification. DHHS publication PHS 91-1260. Washington, DC: United States Department of Health and Human Services, 1991. 9. National Center for Health Statistics. National Hospital Discharge Survey data access system, advanced version, detailed diagnoses and procedures, 1987–1994.Publications PB93-504702, PB93504728, PB93-504744, PB93-504819, PB93-505857, PB94-504537, PB95-503512, PB96-502687. Springfield, VA: National Technical Information Service, 1993–1996. 10. National Center for Health Statistics. 1990 National Hospital Discharge Survey CD-ROM series 13, no. 1. Washington, DC: United States Government Printing Office, 1994. 11. National Center for Health Statistics. Vital health statistics of the United States, Volume I, natality, 1987–1994. Washington, DC: Public Health Service, 1989 –1996. 12. National Center for Health Statistics. 1990 National Hospital
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Discharge Survey public use data tape documentation. Hyattsville, MD: National Center for Health Statistics, 1992. Fleiss JL. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley and Sons, 1981;38 – 45. US Department of Health and Human Services. Healthy people 2000: National health promotion and disease prevention objectives. DHHS publication PHS 91-50212. Washington, DC: US Public Health Service, 1990. Ecker JL, Tan WM, Bansal RK, Bishop JT, Kilpatrick SJ. Is there a benefit to episiotomy at operative vaginal delivery? Observations over ten years in a stable population. Am J Obstet Gynecol 1997;176:411– 4. Helwig JT, Thorp JM, Bowes WA. Does midline episiotomy increase the risk of third- and fourth-degree lacerations in operative vaginal deliveries? Obstet Gynecol 1993;82:276 –9. Peipert JE, Bracken MB. Maternal age: An independent risk factor for cesarean delivery. Obstet Gynecol 1993;81:200 –5. Easterday CL, Grimes DA, Riggs JA. Hysterectomy in the United States. Obstet Gynecol 1983;62:203–12. Layde PM, Fleming D, Greenspan JR, Smith JC, Ory HW. Demographic trends of tubal sterilization in the United States, 1970 –75. Am J Public Health 1980;70:808 –12. Farrow DC, Hunt WC, Samet JM. Geographic variation in the treatment of localized breast cancer. N Engl J Med 1992;326:1097– 101. Ernster VL, Barclay J, Kerlikowske K, Grady D, Henderson C. Incidence of and treatment for ductal carcinoma in situ of the breast. JAMA 1996;275:913– 8. Localio AR, Lawthers AG, Bengston JM, Hebert LE, Weaver SL et al. Relationship between malpractice claims and cesarean delivery. JAMA 1993;269:366 –73.
Address reprint requests to:
Lee A. Learman, MD, PhD Department of Obstetrics and Gynecology–-Room 6D-14 San Francisco General Hospital 1001 Potrero Street San Francisco, CA 94110 E-mail: [email protected]
Received February 17, 1998. Received in revised form May 6, 1998. Accepted May 15, 1998. Copyright © 1998 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
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