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Incidence of histologic types of uterine sarcoma in relation to menstrual and reproductive history

To determine whether the occurrence of one or more histologic types of uterine sarcoma is related to events in a woman's reproductive life, a population‐based case‐control study was conducted. One‐hundred sixty‐seven women newly diagnosed with uterine sarcoma among residents of 6 geographic regions were compared to 208 women selected at random from the same populations with regard to histories of menstruation, pregnancy and childbearing, and breast feeding, as reported during a telephone interview. Compared to women whose menstrual periods began at age 13, women whose menses began earlier were at increased risk of leiomyosarcoma (OR = 2.0, 95% CI 0.9, 4.3); other histologic types were less strongly associated with early age at menarche. Women with leiomyosarcoma and endometrial stromal sarcoma, but not malignant mixed Müllerian tumors, tended to have ceased menstruating 2‐3 years later than controls. None of the histologic types was clearly related to parity or to age at first live birth, but each was inversely related to age at last live birth. Associations were observed between leiomyosarcoma and histories of an induced abortion (OR = 4.2, 95% CI 1.2, 14.2) and of breast feeding after a live birth (OR = 0.5, 95% CI 0.3, 1.0); these relationships were not observed for other morphologic variants. These results suggest possible similarities and differences in menstrual and reproductive risk factors among histologic types of uterine sarcoma, and between these malignancies and the more common breast, endometrial and ovarian carcinomas.