1. Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, PR China
2. The International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, PR China
3. Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Zhengzhou University, Zhengzhou, PR China
4. Department of Preventive Medicine, Henan University of Chinese Medicine, Zhengzhou, PR China
5. Department of Clinical Pharmacology, School of Pharmaceutical Science, Zhengzhou University, Zhengzhou, PR China