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More than 10 million women in the United States have undergone tubal sterilization. There has been concern that this procedure may increase the risk of later menstrual dysfunction. The Collaborative Review of Sterilization (CREST) is a large, multicenter, prospective study of tubal sterilization in the United States. This report describes CREST participants who were interviewed immediately before sterilization and again in annual poststerilization interviews for up to 5 years between 1978 and 1988. The authors analyzed reported changes in six menstrual cycle characteristics for 5,070 women undergoing interval sterilizations. Longitudinal, multivariate regression was used to adjust for baseline menstrual function and other potential confounders. Five years after sterilization, 35% of the CREST participants reported high levels of menstrual pain, 49% reported heavy or very heavy menstrual flow, and 10% reported spotting between periods. In contrast to the fifth year, the first year of follow-up was similar to presterilization menstrual function; in the first year, 27% of participants reported high menstrual pain, 41% reported heavy menstrual flow, and 7% reported spotting. These findings may be affected by aging of the cohort and other study limitations, but they suggest that if tubal sterilization leads to changes in menstrual function, such changes may take some time to develop.

Several hypotheses predict that tubal sterilization and hysterectomy may influence a woman's risk of developing ovarian cancer. To examine the relation between these surgeries and epithelial ovarian cancer, the authors analyzed data from the Cancer and Steroid Hormone Study, a case-control study of women aged 20-54 years. Eight population-based cancer registries in the United States identified women with newly diagnosed epithelial ovarian cancer during 1980-1982 (n = 494). A comparison sample of female residents of these eight areas (n = 4,238) was identified through random digit dialing. Women who had had tubal sterilization (relative risk (RR) = 0.69, 95% confidence interval (Cl) 0.50-0.95), a hysterectomy only (RR = 0.55, 95% Cl 0.38-0.81), or a hysterectomy with unilateral oophorectomy (RR = 0.60, 95% Cl 0.31-1.17) had lower risks of ovarian cancer than did women who had never had any sterilization surgery. However, the negative associations with tubal sterilization and hysterectomy only appeared to wane after two decades. These findings may be partly explained by the screening for occult ovarian pathology that often accompanies pelvic surgery: Women whose ovaries screen as "negative" may be temporarily at low risk of being diagnosed with ovarian cancer. However, because the decreased risks persisted for so long, it is conceivable that hormonal, mechanical, or circulatory sequelae of these sterilization procedures may act to lower ovarian cancer risk.

Studies suggest that hysterectomy and tubal sterilization may alter the function of the remaining ovaries. Conceivably, this effect could alter breast cancer risk. To investigate whether these surgeries affect breast cancer risk, the authors analyzed data collected between December 1, 1980, and April 30, 1983, in a population-based, case-control study of women aged 20-54 years, the Cancer and Steroid Hormone Study. Compared with never-sterilized women, women with hysterectomy and no remaining ovaries had a decreased risk of breast cancer (relative risk (RR) = 0.7, 95% confidence interval (CI) = 0.6-0.8). Risk was lowest in women who had their surgery before age 40 years or 15 or more years in the past; surgery at an early age provided greater protection than surgery in the distant past. Hysterectomy with one or two remaining ovaries was also inversely associated with breast cancer risk (RR = 0.8, 95% CI = 0.7-0.9), but no relation was found with age at surgery or time since surgery. Women with tubal sterilization had a slightly increased risk of breast cancer, which was of borderline statistical significance (RR = 1.2, 95% CI = 1.0-1.3). However, no relation was found with age at surgery or time since surgery. The data suggest that hysterectomy with bilateral oophorectomy decreases the breast cancer risk in women aged less than 55 years, possibly by curtailing ovarian function at a critical period. However, neither hysterectomy without bilateral oophorectomy nor tubal sterilization appears to substantially alter breast cancer risk in women of this age.

The authors examined the relation between cigarette smoking and breast cancer in the Centers for Disease Control Cancer and Steroid Hormone Study, a multicenter, population-based case-control study. The study compared 4,720 women aged 20-54 years with newly diagnosed breast cancer identified through population-based tumor registries with 4,682 women randomly selected from the same geographic areas. Women who reported ever smoking cigarettes had a risk of breast cancer of 1.2 (95 percent confidence interval 1.1-1.3) compared with never smokers. There was no consistent dose-response pattern with any measure of smoking (pack-years of smoking, average number of cigarettes per day, or total years smoked) and little difference in risk between current and former smokers. There was some variation in risk by age, with slightly higher risk estimates for younger women than for older women. Although current smokers had an earlier natural menopause than did never smokers, the authors found no evidence of a protective effect of cigarette smoking on breast cancer risk. These findings suggest that the risk of breast cancer in women who smoke is the same as, or perhaps slightly higher than, women who have never smoked.

Although different definitions of infertility are used, research findings based on various definitions have not been systematically compared. To contrast the impact of five definitions of infertility on research findings, the authors analyzed data from the control group (randomly selected US women aged 20-54 years) of the Cancer and Steroid Hormone Study (1980-1983). For all definitions, an absence of recognized conception was the outcome of interest. Specifically, the authors examined the effect of various definitions of infertility on demographic characteristics of women classified as infertile, prevalence of a history of infertility, age at infertility classification, and cumulative incidence of conception after infertility classification. Results indicated that women classified as infertile by definitions based on unprotected intercourse for 12 months and unprotected intercourse for 24 months were more likely to be black, less educated, and classified as infertile at younger or older ages that women classified by alternative definitions. The prevalence of a history of infertility ranged from 6.1% (physician diagnosis) to 32.6% (unprotected intercourse for 12 months). For the definitions based on unprotected intercourse for 12/24 months and for physician diagnosis, the cumulative incidence of conception by greater than 120 months after infertility classification was 86.3%, 76.7%, and 75.4%, respectively. The authors conclude that the definition of infertility has an impact on research findings related to which and how many women are classified as infertile, the age at infertility classification, and the probability of future conception.