1. Faculty of Forensic Medicine, Zhongshan School of MedicineSun Yat‐sen University Guangzhou P. R. China
2. Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes Guangzhou P. R. China
3. Fetal Medicine Center, Department of Obstetrics and GynecologyThe First Affiliated Hospital of Sun Yat‐sen University Guangzhou P. R. China
4. Department of ObstetricsThe Sixth Affiliated Hospital of Sun Yat‐sen University Guangzhou P. R. China