Evaluating the effects of tubal sterilization on menstrual function: selected issues in data analysis.

We examined selected issues in data analysis in the Collaborative Review of Sterilization (CREST). CREST is a multicentre, prospective, observational study of women undergoing tubal sterilization. We analysed menstrual function after sterilization in over 5000 women who were enrolled in the period 1978-1983 and followed for 5 years with yearly follow-up interviews. To take into account the dependency among repeated responses from the same individuals, we used the generalized estimating equations (GEE) approach to longitudinal data analysis. Marginal modelling resulted in a statistically significant increase in the odds of menstrual dysfunction at 5 years after tubal sterilization. Transitional modelling produced rates of menstrual dysfunction given a woman's menstrual function at baseline, after adjusting for other baseline characteristics such as method of contraception before sterilization. To examine the direction of the bias that could result from non-random missing data, we refitted our models using imputed values. The models with imputed values showed the same trends as the original models.

Menstrual function after tubal sterilization.

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.

PIP: Over 100 Million women worldwide have undergone tubal sterilization. The Collaborative Review of Sterilization (CREST) study at 12 medical centers in the US between 1978-83 examined 5070 women at 4 periodic intervals up to 5 years after the procedure. The purpose was to ascertain whether there were any changes in 6 menstrual cycle characteristics. Several different sterilization methods were examined: unipolar coagulation, bipolar coagulation, silastic band application, spring clips application, partial salpingectomy, and thermocoagulation. Other baseline characteristics which might affect changes in menstrual function over time were examined, i.e., race, body mass index, education, age, gravidity, history of pelvic pathology and pelvic surgery, method contraception immediately preceding sterilization, and incidental pelvic pathology during the sterilization. The presurgery interview included information on baseline menstrual function. The findings from multivariate analysis with unadjusted data showed changes at 5 years but not 2, including increases in menstrual pain, amount of bleeding, and intermenstrual spotting in an amount 1.3-1.8 times greater than those reporting in year 2. There were significant decreases in days/cycle and days of bleeding/cycle for the most women reporting changes. Sterilization method analysis revealed differences between methods for days/cycle, amount of bleeding, menstrual pain, irregularity, and spotting. 33% of women with the spring clip procedure reported increases in menstrual pain. The adjusted model, showed statistically significant differences in cycle length in the 5th year vs. the 1st year, as well as increases in menstrual pain, amount of bleeding, and spotting. Women with the longest cycle lengths in the adjusted analysis used the unipolar coagulation method, and the shortest cycle lengths, the spring clip. Those with the spring clip were also more likely to have menstrual pain and greater bleeding. Black women reported less irregularity and spotting and fewer days of bleeding. Older age at sterilization was related to less pain and greater regularity. The changes in bleeding pattern and menstrual pain are of greatest concern and the most frequently reported in other studies of effects of sterilization. Tissue destruction was found not to be related. Caution is urged in the interpretation of findings. Future research should focus on follow up after 5 years and comparisons with nonsterilized women.

Reducing cesarean sections at a teaching hospital.

A department-wide effort to reduce the cesarean section rate at the University Medical Center of Jacksonville (Florida) began in 1987. University Medical Center, a teaching hospital with approximately 4500 annual deliveries, serves an almost exclusively indigent obstetric population. Overall, the cesarean section rate declined from 28 per 100 deliveries in 1986 to 11 per 100 in 1989. Decreasing the number of repeat cesarean sections played an important role in reducing total cesarean deliveries. In 1986 32% of women with prior cesarean sections underwent a trial of labor. By 1989 this proportion had increased to 84%. In 1986 65% of women undergoing a trial of labor were delivered vaginally. By 1989 this proportion had increased to 83%. For these reasons the proportion of patients who had repeat cesarean sections dropped from 8% in 1986 to 3% in 1989. Changing approaches to the evaluation and management of dystocia and fetal distress also helped to lower the overall cesarean section rate. In 1986 cesarean sections for at least one of these two indications accounted for 14% of all deliveries. By 1989 this percentage had dropped to 4%. Because selective criteria for vaginal delivery of fetuses in breech presentation were maintained, incremental increased rates of vaginal breech delivery had only a minimal impact on lower overall cesarean section rates. The reduction in the number of cesarean sections was accomplished without compromising neonatal outcomes. In fact, during this 4-year period neonatal mortality rates actually decreased; neonatal morbidity rates remained stable. Our experience suggests that cesarean section rates can be substantially reduced without compromising the newborn.

Time series analysis of injuries.

We used time series models in the exploratory and confirmatory analysis of selected fatal injuries in the United States from 1972 to 1983. We built autoregressive integrated moving average (ARIMA) models for monthly, weekly, and daily series of deaths and used these models to generate hypotheses. These deaths resulted from six causes of injuries: motor vehicles, suicides, homicides, falls, drownings, and residential fires. For each cause of injury, we estimated calendar effects on the monthly death counts. We confirmed the significant effect of vehicle miles travelled on motor vehicle fatalities with a transfer function model. Finally, we applied intervention analysis to deaths due to motor vehicles.

Increases in premature mortality due to homicide--United States, 1968-1985.

From 1968 to 1985, the rate of homicide in the United States has increased 44%. Its relative impact on premature mortality, as measured by the percentage of years of potential life lost (YPLL) before age 65 from all causes of death due to homicide, has nearly doubled (93% increase). This increase calls attention to the emerging importance of interpersonal violence relative to all public health problems affecting persons under 65 years of age. The percentage of YPLL from all causes of death due to homicide increased in each race/sex group and for both firearm and nonfirearm means of homicide. The increase in homicide YPLL was traced mainly to an increase in the number of homicide deaths and, to a smaller extent, to a decrease in the average age at death of homicide victims.