Mondo Description A condition occurring in the female offspring of dizygotic twins (twin, dizygotic) in a mixed-sex pregnancy, usually in cattle. Freemartinism can occur in other mammals. When placental fusion between the male and the female fetuses permits the exchange of fetal cells and fetal hormones, testicular hormones from the male fetus can androgenize the female fetus producing a sterile xx/xy chimeric 'female'(chimerism).