Tubal Sterilization among Women of Reproductive Age, United States, Update for 1979-1980

*Vijayakumar I. Moses, M.B.B.S., M.D. George L. Rubin, M.B., F.R.A.C.P. Peter M. Layde, M.D., M.Sc.

Epidemiologic Studies Branch Joyce M. Hughes

Research and Statistics Branch Division of Reproductive Health Center for Health Promotion and Education Introduction

During the past decade, voluntary tubal sterilization emerged as one of the most common methods of fertility control for American women of reproductive age who wished to limit permanently their ability to reproduce. In 1975, CDC began epidemiologic surveillance of tubal sterilization among women of reproductive age in the United States. Statistics for tubal sterilization were published earlier (1-3). This report provides descriptive data on tubal sterilization performed on U.S. women ages 15-44 years in 1979 and 1980 and updates tubal sterilization trends in the period 1970-1980. Materials and Methods

The methods of this study have been described in detail elsewhere (3). Briefly, data used were collected by the National Center for Health Statistics in their National Hospital Discharge Survey (NHDS), which estimates the number and characteristics of patients admitted to U.S. non-Federal, short-stay hospitals for surgical procedures, disease, or injury. Population estimates used in computing rates cited in this report were based on data from the current population surveys conducted by the U.S. Bureau of the Census. *Supported by the Rockefeller Foundation and Centers for Disease Control's International Training Program in Family Planning Evaluation and Epidemiology.

Estimates in this report were rounded to the nearest thousand. Rates, percentages, and averages were calculated from the unrounded estimates and may vary slightly from calculations based on the totals. Data on race were grouped into the categories of white and black for analysis. The latter category includes all races other than white. The percentage of women in 1979 and 1980 in the latter category who were black is not known; however, for the period 1970-1978, 93% were black.

This article focuses on the relationship between tubal sterilization and the following variables:

1. Geographic region of the United States (Northeast, North Central, South, or West--as defined by the Bureau of the Census).

2. Age (15-44 years in 10-year groups).

3. Race (white and black).

4. Timing in relation to pregnancy.

5. Surgical approach (laparoscopy or other).

In order to adequately define the effect of each demographic variable on the rates of tubal sterilization, rates were adjusted for age, race, and geographic region. Because the standardized rates did not differ substantially from the unadjusted rates, only unadjusted rates are presented here. Results

In the period 1970-1980, an estimated 5,526,000 women ages 15-44 years underwent tubal sterilization procedures in U.S. non-Federal, short-stay hospitals (Table 1). Both the number and rate of tubal sterilizations increased steadily from 1970 to a peak in 1977. The rate in 1979 was 12.7/1,000 women ages 15-44, and in 1980 it was 12.4/1,000 women ages 15-44 (Figure 1).

Tubal sterilization rates varied by region in 1979 and 1980 (Figure 2). As in most previous years, women in the South had the highest tubal sterilization rates. Women in the West continued to have the lowest tubal sterilization rates.

In 1979 and 1980, women in the 25- to 34-year age group had the highest tubal sterilization rate (Figure 3). In the same period, the lowest rate was for women in the 15- to 24-year age group, and the intermediate rate was for the 35- to 44-year age group.

As in previous years, the tubal sterilization rate for black women was higher than that for white women in 1979 and 1980 (Figure 4). On the average, for 1979 and 1980, white women were 30 years old and black women were 29 years old at the time of tubal sterilization.

While the number and rate of all tubal sterilizations increased rapidly during the early and mid 1970s, the increase was greater for nonpregnancy-associated sterilizations (those performed on women not pregnant when hospitalized) than for sterilizations performed during hospitalizations to end a pregnancy. For example, in 1970, only 29% of tubal sterilizations were performed on nulliparous women, but by 1976, the percentage had risen to a peak of 58%. This trend did not appear to continue, however, as 49% of sterilizations in 1979 and 47% in 1980 were performed on women who were not pregnant.

In 1979, 31% and 1980, 29% of all tubal sterilizations were performed via laparoscopy, but in those same years 57% and 56%, respectively, of the tubal sterilizations that were not associated with pregnancy termination were performed via laparoscopy. Discussion

The data on tubal sterilization from the NHDS suggest that the number of women hospitalized throughout the nation for tubal sterilizations has decreased since 1977. However, the true rate at which tubal sterilizations are being performed may not be decreasing. From 1970 to 1980, 5.5 million tubal sterilizations and 4.3 million hysterectomies were performed on reproductive-age women in the United States, with a result that considerably more women of reproductive age have had sterilization surgery. The calculations of tubal sterilization rates include in the denominator numbers of women who have had such surgery. If these women are excluded from the denominator, the tubal-sterilization rates rise(4).

Furthermore, increasing numbers of tubal sterilizations may have been performed in freestanding, ambulatory, surgical-care facilities, hospital outpatient facilities, or Federally operated hospitals such as Armed Forces and Public Health Service hospitals. No data on such procedures are included in the NHDS analysis. A recent survey suggested that in 1980 approximately 16,500 tubal sterilizations were performed nationwide in freestanding ambulatory surgical-care facilities (5). To this extent and to the extent that more tubal-sterilization procedures are performed in other outpatient facilities, the NHDS data will increasingly underestimate the actual number and rates of tubal sterilizations being performed in the United States.

The difference in tubal-sterilization rates for white women vs. black women may be explained by the higher parity of women in the latter groups over that for white women (6) and by the fact that vasectomy is a more frequently chosen method of contraceptive sterilization by white couples than by black couples (7).

Regionally, women in the western United States had considerably lower tubal-sterilization rates than those in other regions. That vasectomy is a more frequently selected sterilization option by couples in the West may account for some of this difference (7). That women in the South had the highest tubal-sterilization rate in the country may in part reflect increased age-specific parity (6) among southern women of all races.

In conclusion, these data demonstrate that there was a decrease in numbers of women admitted to hospitals for tubal sterilizations in 1979 and 1980. Moreover, substantial differences in the rates reflect interregional and racial differences that persist, with the lowest rates in the West and with black women having higher tubal-sterilization rates than those for white women. The number of tubal sterilizations performed in outpatient clinics and Federally funded hospitals must be determined in order to fully document the use of tubal sterilization in the United States.

References

1. CDC. Surgical sterilization surveillance; tubal sterilization 1970-1975. Atlanta, Ga.: Center for Disease Control, 1979.

2. CDC. Surgical sterilization surveillance; tubal sterilization 1976-1978. Atlanta, Ga.: Centers for Disease Control, 1981.

3. CDC. Surgical sterilization surveillance; tubal sterilization 1979-1980. Atlanta, Ga.: Centers for Disease Control (in press).

4. Nolan TF, Ory HW, Layde PM, Hughes JM, Greenspan JR. Cumulative prevalence rates and corrected incidence rates of surgical sterilization among women in the United States, 1971-1978. Am J Epi 1982;116:776-81.

5. Greenspan JR, Rubin GL, et al. Tubal sterilizations performed in freestanding ambulatory surgical care facilities, J Reprod Med 1983 (in press).

6. U.S. Bureau of the Census. Current population reports, series P-20, No. 375. Fertility of American women: June 1980. Washington, D.C.: U.S. Government Printing Office, 1979.

7. Westoff CF, McCarthy J. Sterilization in the United States. Fam Plann Perspect 1979;11:147-52. Table 1.Tubal sterilizations* for women ages 15-44 years, by race, age, geographic region, and timing in relation to pregnancy, United States, 1970-1980

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