Objective: To examine patterns of hysterectomy in the Oxford-Family Planning Association (Oxford-FPA) study in relation to age, parity, social class and calendar period (-1974, 1975-79. 1980-84, 1985-89).
Design: The Oxford-FPA study is a large scale prospective study of 17,032 women recruited from 1968-74 and still under observation.
Setting: Seventeen family planning centres throughout England and Scotland.
Subjects: At recruitment the 17,032 women were all white, British, married, aged 25-39 and willing to co-operate. In addition, they were using the pill or an intrauterine device or a diaphragm as their method of contraception.
Main outcome measure: Hysterectomy rates per 1000 woman-years of observation in various subclasses of the data.
Results: Up to the end of 1989, 1885 (11.1%) of the 17,032 women in the study were known to have undergone hysterectomy. Fibroids were the most common cause followed closely by menstrual disturbances in the absence of fibroids (hereafter referred to as 'menstrual disturbances'). Social class had a modest influence on hysterectomy rates. Hysterectomy for fibroids, prolapse, endometriosis and 'other reasons' showed little trend with calendar period while hysterectomy for menstrual disturbances and for cancer showed a sharp increase with calendar time especially at ages 30-39. Hysterectomy generally tended to increase with age and showed a strong relation to parity; in particular, hysterectomy for fibroids fell with parity and hysterectomy for menstrual disturbances rose sharply with parity. Using lifetable methods, it was estimated that almost 20% of the women in the study would have had a hysterectomy by age 55.
Conclusions: The results give insights into factors affecting hysterectomy rates. Of particular interest is the modest influence of social class, the strong influence of parity and the rise in rates with calendar time at ages 30-39 for those undergoing hysterectomy for menstrual disturbances or cancer, but since the cohort is not directly representative of the population, some caution is required in extrapolating these findings. The estimated hysterectomy rate of about 20% by age 55 is in line with other similar estimates for the United Kingdom.