Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Science, Beijing, 100730, China. Zhengzhou Central Hospital Affiliated to Zhengzhou University, No. 16 Tongbai North Road, Zhongyuan District, Zhengzhou, Henan Province 450007, China. Shenyang Maternity and Child Health Hospital, No. 41 Shenzhou Road, Shenhe District, Shenyang, Liaoning Province 110000, China. QuanZhou Women's and Children's Hospital, No. 700 Fengze Street, Quanzhou, Fujian Province 362000, China. Shenyang Women's and Children's Hospital, No. 87 Danan Street, Shenhe District, Shenyang, Liaoning Province 110011, China. Xiamen Maternal and Child Health Hospital, No. 10 Zhenhai Road, Xiamen, Fujian Province 361003, China. Shunyi Women's & Children's Hospital of Beijing Children's Hospital, No. 1 Shunkang Road, Shunyi District, Beijing 101300, China. Jinan Maternity and Child Care Hospital Affiliated to Shandong First Medical University, No. 2 Jianguoxiaojingsan Street, Shizhong District, Jinan, Shandong Province 250001, China. Fuyang People's Hospital, No. 63 Luci Street, Yinzhou District, Fuyang, Anhui Province 236004, China. Beijing Pinggu Hospital, No. 59 Xinping North Road, Pinggu District, Beijing 101200, China. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Science, Beijing, 100730, China. Electronic address: MaLiangKun@pumch.cn.