1. From the Department of Medical Ultrasonics (K.Y., Y.J.H., M.Y.M., S.J.W., D.N.H., W.F.L., X.M.Z., X.Y.C., Y.X.Z.) and Department of Obstetrics and Gynecology (T.L., M.X.L.), The Seventh Affiliated Hospital of Sun Yat-Sen University, 628 Zhenyuan Road, Xinhu Street, Guangming District, Shenzhen 518107, People’s Republic of China.