1. Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou 511436, China
2. Section of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Yale School of Medicine, Yale University, New Haven, CT 06520–8057, U.S.A.
3. Department of Clinical Laboratory Medicine, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China
4. Key Laboratory for Major Obstetric Diseases of Guangdong Province, Guangzhou 510150, China
5. Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, Guangzhou 510150, China