1. Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu, China
2. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
3. Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, China
4. Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden