1. Qingdao Women and Children’s Hospital, Qingdao University School of Medicine, Qingdao, PR China
2. Division of Fetal Medicine, Department of Obstetrics, Leiden University Medical Center, Leiden, The Netherlands
3. Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, The Netherlands
4. Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, PR China