1. From the Departments of Obstetrics, Gynecology, and Reproductive Biology (E.R.N., L.P.J.H., D.R.-T., L.W.-H.) and Radiology (P.R., C.M.C.T.), Brigham and Women's Hospital and Harvard Medical School; and the Departments of Cardiology (K.J.J., M.E.V.) and Surgery (S.J.F.), Children's Hospital and Harvard Medical School — all in Boston.