1. Department of Obstetrics and Gynecology (P.S.N.L., B.H.Y., P.C.K.L.), University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5
2. Department of Physiology (A.M.J.B.), University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5
3. Division of Reproductive Biology, Stanford University Medical Center (A.J.W.H.), Stanford, California 94305