Fetal antigen hypothesis and ovarian cancer: is there an immunogenic explanation for the reduction in risk associated with parity?

The hypothesis that a woman's immunologic response to fetal antigens arising from paternal genes may explain some of the reduction in risk of ovarian cancer associated with parity has not, to our knowledge, been examined. We analyzed data from a case-control study to evaluate the risk of epithelial ovarian cancer among women of similar parity associated with proposed indices of paternally derived fetal antigen exposure. Cases included white women 20-79 years of age diagnosed with epithelial ovarian cancer in three counties in Washington State between January 1, 1986, and December 31, 1988 (N = 322). Controls (N = 426) were selected by random-digit dialing and were broadly similar to cases in age and county of residence. After excluding women who had fewer than two pregnancies (or, in some analyses, fewer than two livebirths) and adjusting for age and number of livebirths, we observed no reduction in risk associated with number of marriages or number of partners with whom a study participant conceived a pregnancy and/or had a child. Nevertheless, these relatively crude indices of exposure to paternally derived fetal antigens do not preclude the possibility that a woman's response to other fetal or pregnancy-related antigens may antagonize the development of ovarian cancer.