1. Department of Child, Adolescent Health and Maternal Care, School of Public Health, Capital Medical University, Beijing 100069, China
2. Department of Growth and Development, Capital Institute of Pediatrics, Beijing 100020, China
3. Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
4. Department of Echocardiography, Beijing Anzhen Hospital, Capital Medical University, Beijing 100029, China
5. Yale School of Public Health, Yale University, New Haven, CT 06510-3201, USA
6. Department of Hematology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China