1. Department of Ultrasonic Medicine Fetal Medical Center the First Affiliated Hospital of Sun Yat‐sen University Guangzhou China
2. Fetal Medicine Unit St George's Hospital and Vascular Biology Research CentreMolecular and Clinical Sciences Research InstituteSt George's HospitalUniversity of London London UK
3. Department of Biostatistics Unit Oncology Research Laboratory the Cancer Hospital of Shantou University Medical College Guangdong China