INCOMPLETE PREGNANCIES AND RISK OF OVARIAN-CANCER (WASHINGTON, UNITED-STATES)

Because of the reduced risk of ovarian cancer related to prior full-te rm pregnancies, we sought to determine whether there was any associati on with a history of one or more incomplete pregnancies. White female residents of three counties in Washington State (United States) diagno sed with ovarian cancer during 1986-88 (n = 322), and a random sample of control women selected from these same counties (n = 426), were int erviewed regarding their pregnancy and childbearing histories. Among w omen who had given birth to at least one child, an additional incomple te pregnancy was not associated with the risk of ovarian cancer (relat ive risk [RR] = 1.1, 95 percent confidence interval [CI] = 0.8-1.6, ad justing for age, oral contraceptive use, and number of births). For th ose who had never given birth, a somewhat smaller proportion of cases had a history of incomplete pregnancy than controls (RR = 0.8, CI = 0. 4-1.7). In an analysis restricted to ever-pregnant women, a prior indu ced or spontaneous abortion was not found to be associated with the in cidence of ovarian tumors (RR = 1.0, CI = 0.6-1.7, and RR = 1.3, CI = 0.8-1.9, respectively), Other studies of the possible relation between incomplete pregnancies and ovarian cancer generally have observed eit her a weak negative association or no association at ah. It is possibl e that if incomplete pregnancies do affect the risk of ovarian cancer, their impact might be too small to be identified reliably through epi demiologic studies.