From the Departments of Obstetrics and Gynecology and Medicine, Northwestern University Medical School and Passavant Memorial Hospital, Chicago, Ill.

^*Josiah Macy, Jr., Foundation Fellow in Reproduction for medical students.

Supported in part by the Lucy and Edwin Kretchmer Fund of Northwestern University and by a grant from the Chicago Heart Association and U.S.P.H.S. Grant H-1890.

We wish to thank Mrs. Jolanta Munch for her technical assistance in this study.

Submitted for publication March 10, 1961.