Trends in cesarean section use in California, 1983 to 1990

Randall S. Stafford, PhD," Sean D. Sullivan, PhD,b and Laura B. Gardner, MD, MPH, PhDc

San Francisco, Menlo Park, and San Jose, California, and Seattle, Washington

OBJECTIVE: Our aim was to assess recent trends in cesarean section use in California. STUDY DESIGN: California discharge abstract data on hospital deliveries in 1983 through 1990 (379,759 to 587,508 annual deliveries) were used to analyze time trends by indication, age, race, and payment source. RESULTS: California cesarean section rates increased annually from 21 .8% in 1983 to 25.0% in 1987 and then decreased to 22.7% by 1990. Similar patterns were noted for all age and race or ethnicity groups. Primary cesarean section rates increased from 15.2% in 1983 to 17.9% in 1987, then decreased to 16.2% by 1990. Declines in repeat cesarean section rates continued throughout 1983 through 1990, accelerating after 1987. For both primary and repeat cesarean section rates, time trends after mid-1987 were significantly different than those for 1983 to 1987. CONCLUSION: After increasing from 1983 to 1987, California cesarean section rates declined from 1988 to 1990. Existing payment source differences in cesarean section use increased in magnitude from 1983 to 1990, with privately insured women consistently having the highest cesarean section rates. (AM J OBSTET GVNECOL 1993; 168: 1297-302.)

Key words: Cesarean section, time trends, payment source, hospital discharge abstracts

Between 1970 and 1988 cesarean section rates in the United States more than quadrupled, from 5.5% to 24.7%.1. 2 The dramatic rise in this relatively costly surgical procedure has prompted concern regarding current obstetric practices. Calls for reductions in ce­sarean section rates have been prompted by evidence suggesting that (1) excellent perinatal outcome can be achieved with relatively low cesarean section use,'·5 (2) considerable variations in cesarean section rates are associated with nonclinical factors,6.8 and (3) hospital­initiated programs have reduced cesarean section use successfully.9. 10

Beginning with a National Institutes of Health con­sensus conference in 1981, increasing attention has been focused on reducing cesarean section use. In spite of many policy recommendations 11 .13 both within and outside the obstetrics specialty, cesarean section rates in the early 1980s continued to increase. Informed esti­mates have suggested that national cesarean section rates now may be declining! perhaps in response to

From the School of Medicine, University of California, San Fran­cisco, a the Schools of Pharmacy and Public Health, University of Washington: the Health Policy Research Program, SRI Interna­tional, and the Department of Health Sciences, San Jose State University. ' Supported by grant No. HS 06642-01 from the Agency for Health Care Policy and Research, United States Public Health Service. Received for publication April 8, 1992; revised August 31, 1992; accepted October 22, 1992. Reprint requests: Laura B. Gardner, MD, MPH, PhD, Health Policy Research Program, BN112, SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025. Copyright © 1993 by Mosby-Year Book, Inc. 0002-9378/93 $1.00 + .20 6/1/43663

increasingly strong policy interventions aimed at reduc­ing cesarean section use.

Recent data on cesarean section use are necessary to assess whether cesarean section rates have continued to increase or are now declining. Although it is difficult to identify specific causes of changing practice patterns, a detailed analysis of time trends may indicate the aggre­gate influence of policy strategies. In addition, the extent to which recent changes vary across clinical and sociodemographic sub populations may help determine future policy strategies. This report analyzes cesarean section rates among California hospital deliveries, fo­cusing on time trends in cesarean section rate differ­ences by payment source.

Material and methods

This analysis used hospital discharge abstract data available from the California Office of Statewide Health Planning and Development for calendar years 1983 through 1990. Over this period annual nonmilitary hospital deliveries increased from 379,759 in 1983 to 587,508 in 1990. Diagnosis-related group codes were used to distinguish vaginal (codes 370 to 371) from cesarean deliveries (372 to 375). Cesarean section rates were calculated as the number of cesarean deliveries per 100 deliveries.

Calculations of repeat and primary cesarean section rates were based on women with and without a coded history of previous cesarean section (International Clas­sification of Diseases, ninth revision, clinical modifica­tion code 642.6),14 respectively. Information on trial of labor and past obstetric history was not available. Rates were calculated by race or ethnicity groups (white, Hispanic, black, Asian, and others/unknown) and by

1297

1298 Stafford, Sullivan, and Gardner

Table I. Regression results

April 1993 Am J Obstet Gynecol

Monthly rate primary cesarean sections (n = 95 mo)

Monthly rate repeat cesarean sections (n = 95 mo)

Variable

Constant Time trend (january 1983 = 1) Dummy ( = 1 if time 2: 53) Dummy ( = 1 if time 2: 62) Interaction term (time' dummy [xl) Adjusted multiple R Fvalue

N/A. Not available.

Coefficient (t statistic)

0.14521 (162.9) 0.00068 (23.3) 0.06869 (15.5)

N/A -0.00131 (18.87)

0.902 251.226

I Significance

p < 0.0001 P < 0.0001 P < 0.0001

P < 0.0001

P < 0.0001

Coefficient (t statistic)

0.93484 (564.5) - 0.00108 (23.2)

N/A 0.20646 (13.1)

-0.00345 (15.7) 0.980

1354.954

I Significance

p < 0.0001 P < 0.0001

P < 0.0001 P < 0.0001

P < 0.0001

Table II. Percentage of deliveries by age group, race-ethnicity, and previous cesarean section, California, 1983 to 1990

Percentage by age group Total

<25 I 25-34 I White I deliveries 35+

1983 379,759 41.6 50.9 7.5 55.4 1984 405,011 40.6 51.5 7.9 55.4 1985 415,909 39.5 52.1 8.4 52.0 1986 461,471 38.9 52.2 8.9 52.5 1987 483,235 37.8 52.7 9.5 51.5 1988 513,708 37.1 52.9 10.0 49.6 1989 545,817 37.3 52.4 10.3 47.3 1990 587,508 37.6 51.7 10.7 44.8

age group « 25, 25 to 34, and 2: 35 years). Expected source of payment for each delivery was analyzed for six payment categories: (1) Medi-Cal (the California Med­icaid program), (2) the Kaiser Permanente health main­tenance organization, (3) private insurance, (4) non­Kaiser health maintenance organizations, (5) self-pay and indigent services, and (6) all other payers.

To assess the statistical significance of changing pat­terns of cesarean section use, we developed separate linear time series regression models for monthly pri­mary and repeat cesarean section rates. With monthly cesarean section rates for January 1983 through De­cember 1990, we evaluated whether the most recent time trends differed statistically from earlier trends.

Regression analysis was performed on monthly deliv­ery data for both primary and repeat cesarean rates. A simple multivariate time series model was specified to estimate the annualized trend in cesarean section rates and to test for differences between pre- and post-1987 trends in rates. A shift (dummy) variable was used in both models to account for intercept differences before and after 1987. Through an iterative process we deter­mined the particular month for each model where accounting for before and after effects yielded the best statistical fit.

The monthly dummy variable specification was cho-

Percentage by Percentage by race-ethnicity previous cesarean

Black I Hispanic I Asian I Other No 1 Yes

8.2 25.1 6.6 4.7 91.4 8.6 7.9 26.7 6.6 3.4 90.8 9.2 8.4 29.2 7.4 3.0 90.8 9.2 8.1 29.6 7.2 2.6 90.2 9.8 8.2 30.0 7.6 2.7 89.9 10.2 8.0 31.7 8.0 2.7 89.3 10.7 7.9 34.4 7.6 2.8 89.2 10.8 7.4 37.7 8.1 2.0 88.9 ILl

sen by means of sensitivity analysis with the decision rule based on precision of model fit measured by maximization of the F value. An interaction term, de­fined as the product of the time trend and the monthly shift variable, was used to estimate trend differences between the two periods. Regression coefficients were calculated to assess the effect of time on cesarean section rates for (1) the entire 1983 to 1990 time period and (2) any additional effect of time observable after the identified month. A statistically significant coefficient for the more recent time period indicates that recent trends differ from earlier trends. Table I presents the results.

ResuHs

From 1983 to 1990 the annual number of hospital deliveries in California increased by 55%. Simulta­neously there was an inuease in the proportion of deliveries to women 2: 35 years old (from 7.5% in 1983 to 10.7% in 1990), to Hispanic women (from 25.1% in 1983 to 37.7% in 1990), and to women with previous cesarean sections (from 8.6% in 1983 to 11.1 % in 1990) (Table II).

Consistent with a long-standing trend, total Califor­nia cesarean section rates increased from 21.8% of all deliveries in 1983 to 25.0% in 1987. Mter 1987, how-

Volume 168, Number 4 Am J Obstet Gynecol

Stafford, Sullivan, and Gardner 1299

Primary Cesarean Section Rate (%)

18

17

16

15

, , .. . .,

Month/Year

Fig. 1. Monthly primary cesarean section rates, California, 1983 to 1990. Best-fit regression models based on time trends before and after April 1987. There is statistically significant difference in rate of change before and after this date (p < 0.0001).

Table III. Cesarean section rates per hundred deliveries, by age group, race-ethnicity, and indication, California, 1983 to 1990

Age group Race-ethnicity Indication

Total <25 I 25-34 I 35+ White I Black I Hispanic I Asian I Other Primary I Repeat

1983 21.8 18.5 23.5 29.0 23.2 1984 22.6 19.2 24.3 29.5 24.1 1985 23.3 19.4 24.9 30.7 25.0 1986 24.5 20.5 26.2 32.1 26.3 1987 25.0 21.0 26.5 32.6 26.8 1988 24.2 19.6 25.9 32.4 26.1 1989 23.2 18.8 24.8 31.1 25.2 1990 22.7 18.1 24.4 30.9 25.0

ever, cesarean section rates declined, to 24.2% in 1988, 23.2% in 1989, and 22.7% in 1990 (Table III).

Identical patterns of increasing cesarean section rates until 1987 and then declining rates through 1990 were noted for each maternal age group. For example, women < 25 years old showed the following pattern: 18.5% in 1983,21.0% in 1987, and 18.1% in 1990. For women ;;:: 35 years old the pattern was 29.0% in 1983, 32.6% in 1987, and 30.9% in 1990 (Table III). Similar patterns also were noted for each race and ethnicity group. Cesarean section rates for whites increased from 23.2% in 1983 to 26.8% in 1987 and then decreased to 25.0% in 1990. Hispanics showed a similar pattern: 18.9% in 1983, 22.4% in 1987, and 20.0% in 1990 (Table III).

This same pattern also was noted for women without a previous cesarean section, where primary cesarean section rates increased from 15.2% in 1983 to 17.9% in 1987 and then declined to 16.2% in 1990.

24.3 18.9 19.8 21.2 15.2 92.7 24.3 19.9 20.4 20.9 15.7 91.4 24.7 20.5 20.8 22.2 16.5 89.6 25.9 21.7 22.5 22.9 17.5 89.1 26.3 22.4 22.7 23.8 17.9 87.5 25.7 21.4 22.4 23.5 17.0 84.2 25.7 20.1 21.6 23.5 16.4 78.7 25.0 20.0 20.9 22.0 16.2 75.3

The statistical analysis indicates that primary cesar­ean rates were increasing at an annualized rate of 0.82% before May 1987, then decreasing 0.76% per year thereafter (Fig. 1). Analysis of monthly repeat cesarean rates (Fig. 2) indicates a secular decline of l.30% per year before January 1988 and a higher rate of decline, 5.44% per year, thereafter.

Hospital deliveries in California are reimbursed by a heterogeneous set of health care payers. The California Medicaid program (Medi-Cal) accounted for the great­est proportion of deliveries (39.0% in 1990); most of the rest were financed by private insurance (20.8%), non­Kaiser health maintenance organizations (19.2%), the Kaiser Permanente health maintenance organization (10.5%), and self-payor indigent services (8.1%) (Table IV). There has been a substantial increase in the share of deliveries reimbursed by non-Kaiser health mainte­nance organizations (from 4.3% of deliveries in 1983 to 19.2% in 1990).

1300 Stafford, Sullivan, and Gardner

Repeat Cesarean Section Rate (~)

.... . . ' . 92 .....••.•... ; ... ~ ...

.' . .. . . . ..... . 87

77

.1 .. , ,

..... .... .. : ........• , : ..... , , .,

, .......... 1 .... , ... -.-

April 1993 Am J Obstet Gynecol

Month/Year

Fig. 2. Monthly repeat cesarean section rates, California, 1983 to 1990. Best-fit regression models based on time trends before and after January 1988. There is statistically significant difference in rate of change before and after this date (p < 0.0001).

Table IV. Percentage of deliveries and cesarean section rates per hundred deliveries, by payment source, California, 1983 to 1990

Percentage of deliveries

Non-Kaiser health

maintenance Medi-Private organization Cal Self-pay-indigent Kaiser Others

1983 40.1 4.3 24.4 12.7 12.9 1984 39.7 6.0 26.3 12.1 12.2 1985 37.0 7.9 25.6 13.4 12.5 1986 35.1 10.0 26.7 12.9 11.2 1987 33.2 12.5 27.2 12.1 10.8 1988 29.4 15.6 29.4 11.2 10.8 1989 24.7 17.7 34.6 9.1 11.0 1990 20.8 19.2 39.0 8.1 10.5

Large differences in cesarean section rates by pay­ment source were noted from 1983 through 1990. Women with private insurance had the highest rates: 26.0% in 1983, 29.4% in 1987, and 28.5% in 1990. Women covered by the Kaiser health maintenance or­ganization had substantially lower rates: 18.0% in 1983, 19.8% in 1987, and 18.3% in 1990. Relatively low rates also were noted for Medi-Cal and self-payor indigent categories. The ratio of private insurance to Kaiser total cesarean section rates increased from 1.44 in 1983 to 1.48 in 1987 and to 1.56 in 1990 (fable IV). This divergence was more pronounced for repeat cesarean section rates, where the ratio of private insurance to Kaiser increased from 1.11 in 1983 (private insurance 95.8% vs Kaiser 86.3%) to 1.18 in 1987 (90.3% vs 76.7%) and to 1.36 in 1989 (83.9% vs 61.5%).

5.6 3.7 3.6 4.1 4.2 3.6 2.9 2.4

Cesarean section rates

Non·Kaiser health

maintenance Medi-Private organization Cal Self-pay-indigent Kaiser Others

26.0 22.7 20.8 15.2 18.0 19.1 26.7 23.6 21.2 17.1 18.7 18.0 27.8 24.8 21.9 17.6 18.8 19.0 29.1 26.9 23.0 18.7 19.7 20.3 29.4 27.7 23.4 19.6 19.8 21.5 29.2 27.2 21.8 18.7 19.1 22.7 28.7 26.5 20.2 18.7 18.1 24.5 28.5 26.3 19.9 18.3 18.3 25.0

Comment

Contrary to expectations that cesarean section rates would continue to climb,15 we find that they have recently declined in California. This pivotal change may reflect many factors but is likely to represent the success of policy strategies aimed at reducing cesarean section rates. The decline has occurred in spite of an increasing number of deliveries to older women and to women with previous cesarean sections. Declining cesarean sec­tion rates from 1987 to 1990 were noted across all race or ethnicity and maternal age groups. Repeat cesarean section rates declined through the entire 1983 to 1990 period, but the rate of decline accelerated after 1987. Primary cesarean section rates, which had increased up to 1987, declined after mid-1987. Whatever factors have produced this change in practice patterns have

Volume 168, Number 4 Am J Obstet Gynecol

Primary Cesarean Section Rate (%)

22

21

20

19

18

17

16

15

~: .: .... /~ ...... :

13 15

. ' ~ ... -..... .

.'

17

Stafford, Sullivan, and Gardner 1301

...... - .... -..... ..

II ., Month/Year

Fig. 3. Monthly primary cesarean section rates of privately insured patients compared with all others, California, 1983 to 1990.

Repeat Cesarean Section Rate (%) 98~~------------------------------------------~

96 #'tt+'* -t, ~-ft + 94 92 90 88 86 84 82 80 78 76 74 72

-t:+ 4- th:..+ + ~+ ##}--fl*i- +

'.~"., + + +' £+-+:1t " ...... : • ....,.. + +W+..J,<.+ . ..... .,~

" .'. ..... ~+ ••••• ........ +tt- +

All Other PaY0rl

". +4f+!ft:++ + '" ++-1-;

'. •• ····.11· .

+ Private Payon I.

...... :tr:+-+

+ -....

"." .-70~~~~llil~~Uli~~~LW~~~Ull~~~~Uli~~liD~~

13 14 15 17 II .,

" Month/Year

Fig. 4. Monthly repeat cesarean section rates of privately insured patients compared with all others, California, 1983 to 1990.

not been confined to specific demographic subpopula­tions, consistent with the global effect of most policy initiatives. Among speculative reasons for the change in practice patterns are (1) changing reimbursement pol­icies of insurers, especially the state Medicaid pro­gram,16 (2) the well publicized publication of several articles critical of high cesarean section rates,5. 9 and (3) increasing public awareness of cesarean section prac­tices.

Although we have developed a model that distin­guishes trends before and after a particular point in

time, the data do not necessarily suggest that any specific event was responsible for the change. More likely, the results represent a complex process of diffu­sion of innovation. 17·19 Medical practice is usually rela­tively slow to change in response to clinical research findings, in part because mechanisms for the coordi­nated dissemination of research are lacking. In addi­tion, practice patterns are often anchored in the norms and conventions of local relationships and may change only through hospital-by-hospital incorporation of new practices into a formal or informal consensus among

1302 Stafford, Sullivan, and Gardner

the medical staff. Diffusion of innovation - in this case the use of more conseIVative indications for performing cesarean section - may be influenced by various organi­zational characteristics, including predisposing, en­abling, and reinforcing factors. 19

Mechanisms of reimbursement appear to be one such predisposing factor. In spite of declining cesarean sec­tion rates, differences in rates by payment source have not only persisted but increased. Those payers with low initial rates (Kaiser, Medi-Cal, and self-payor indigent seIVices) declined most strikingly between 1987 and 1990. Although further analysis is needed to account fully for the various factors known to influence cesarean section rates,7 the obseIVed impact of nonclinical factors suggests a heightened importance of economic and organizational factors in clinical decision making. The data suggest that, as a large, centralized health main­tenance organization, Kaiser may have responded more readily to changes in financial incentives, professional recommendations, or public concerns regarding in­creasing use of cesarean section delivery.

Additional support for the effect of organizational and reimbursement factors on cesarean section rates can be found in the widening variance in rates, both primary (Fig. 3) and repeat (Fig. 4), between privately insured patients and all others. A related analysis that was performed to account simultaneously for a large number of factors found that both the patient's source of payment and the hospital's ownership category had significant, independent associations with cesarean sec­tion rates, controlling for the patient's clinical risk!O Further exploration of factors associated with cesarean section rate variations is in progress.

On the basis of the uniform decline in cesarean section rates across demographic groups, we would expect continuing decreases in these rates. This study'S use of an administrative data source carries the limita­tion that the quality of diagnostic coding may not be optimal. Quality of coding is most likely to affect the distinction between primary and repeat cesarean sec­tion rates, where previous cesarean section may not be reported consistently.

The persistence in payment source differences in cesarean section use suggests a continuing need for policy inteIVention. One particular focus should be on the providers and hospitals seIVing privately insured women. The continuing high rates of cesarean section in this group of women suggest the potential for further reductions.

April 1993 Am J Obstet Gynecol

We thank Loren C. Rauch for research assistance in the analysis of data for this article.

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9. Myers SA, Gleicher N. A successful program to lower cesarean section rates. N Engl J Med 1988;319:1511-6.

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II. Cesarean childbirth: report of the NICHD Task Force on Cesarean Childbirth. Bethesda, Maryland: National Insti­tutes of Health, 1981; DHHS publication no (NIH) 82-2067.

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16. California Medical Assistance Program. Medi-Cal Direc­tive, September 1987. Sacramento: State of California, Department of Health Services, 1987.

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