Peking Union Medical College Hospital;
Chinese Academy of Medical Sciences;
Beijing 100730;
China;
Cincinnati Children's Hospital Medical Center';
Cincinnati;
Ohio 45229;
USA;
Tongzhou Maternal & Child Health Hospital of Beijing;
Beijing 101100;
China;
Peking University People's Hospital;
Beijing 100044;
China;
Beijing Chao-Yang Hospital;
Capital Medical University;
Beijing 100020;
China;
Peking University First Hospital;
Beijing 100034;
China;
Peking University Third Hospital;
Beijing 100191;
China;
Beijing Obstetrics and Gynecology Hospital;
Capital Medical University;
Beijing 100006;
China;