1. Department of Obstetrics and Gynaecology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand;
2. Reproductive Endocrinology and Infertility Unit, Department of Obstetrics and Gynaecology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand;
3. Section for Clinical Epidemiology and Biostatistics, Faculty of Medicine Ramathibodi, Mahidol University, Bangkok, Thailand