AN EPIDEMIOLOGIC STUDY OF THE RELATIONSHIP OF REPRODUCTIVE EXPERIENCE TO CANCER OF THE OVARY1

Abstract

From June 1957 to September 1965, all patients entering the Roswell Park Memorial Institute in Buffalo, New York, completed a questionnaire providing detailed information on demographic and social attributes, family history, radiation exposure, menstrual and reproductive characteristics and personal habits. Over 400 cases of ovarian cancer were admitted. These, combined with control groups consisting of patients with other cancers (colo-rectum and breast) and with non-neoplastic diseases, formed the basis of the current study. The findings in this study showed that women with ovarian cancer had the following characteristics: 1) a lower mean number of pregnancies, even when pregnancy rates were calculated per 1000 person-years at risk of the event; 2) a larger proportion of never-pregnant and ever-pregnant women with one or two conceptions; 3) an increase in the relative risk of cancer of the ovary as the total number of pregnancies decreases; 4) a greater risk of ovarian cancer in ever married-never pregnant than in never-married women; 5) a late age at first pregnancy, except in the comparison with breast cancer controls; 6) a greater interval between first marriage and first conception; 7) a greater difference with their mothers in completed sibship size; 8) a larger proportion of women who tried and failed to become pregnant at least once; and 9) an increase in the frequency of conceptions terminating as miscarriages. Several explanations for these findings were considered. It was generally felt that the results indicated that women who developed ovarian cancer had a gonadal status that predisposed to both the ovarian cancer and the low fertility.