[1] Sun Yat Sen Univ, Affiliated Hosp 3, Dept Obstet & Gynecol, Guangzhou 510630, Guangdong, Peoples R China
[2] Temple Univ, Dept Biol, Philadelphia, PA 19122 USA
[3] Shanghai Publ Hlth Clin Ctr, Dept Obstet & Gynecol, Shanghai, Peoples R China
[4] Fudan Univ, Publ Hlth Clin Ctr, Shanghai 200433, Peoples R China
[5] Guangzhou Med Coll, Affiliated Hosp 3, Dept Obstet & Gynecol, Guangzhou, Guangdong, Peoples R China