Estrogen antibodies reduce vulnerability to stress-induced failure of intrauterine implantation in inseminated mice

In Experiment 1, inseminated mice were randomly assigned to either an undisturbed control condition or four conditions involving exposure to restraint stress on days 1 through 5 of pregnancy. Restrained animals received one of three doses of estrogen antibodies or just vehicle injections on each day of restraint. Restrained animals receiving vehicle only showed significantly fewer uterine implantation sites than did unrestrained controls, while restrained animals given estrogen antibodies showed more implantation sites than did vehicle-treated restrained animals. In Experiment 2, varied dosages of refined estrogen antibodies were administered to inseminated females concurrent to restraint-stress on days 1 through 5 of pregnancy. More females receiving the higher dosages of antibodies produced litters than did restrained females with just vehicle injections, and at the highest dose the number of litters was similar to that produced by undisturbed control females. These results converge with other evidence to suggest that stress-induced pregnancy blocks are mediated by estrogens.