1. Department of Obstetrics and Gynecology (H.H., T.S.-F., Y.H., M.E., L.M., M.M., T.H., K.K., T.F., Y.O.), the University of Tokyo, Tokyo 113-8655, Japan;
2. Precursory Research for Embryonic Science and Technology (Y.H.), Japan Science and Technology Agency, Saitama 332-0012, Japan;
3. Graduate School of Agricultural and Life Sciences (M.E.); the University of Tokyo, Tokyo 113-8655, Japan;
4. Department of Pathology (N.Y., M.F.), Graduate School of Medicine; Department of Veterinary Medical Sciences, the University of Tokyo, Tokyo 113-8655, Japan;
5. Division of Reproductive Sciences (A.B., J.C., S.K.D.), Perinatal Institute, Cincinnati Children's Research Foundation, Cincinnati, Ohio 45229