1. Department of Medicine; Faculty of Medicine; Thammasat University
2. Department of Obstetrics and Gynecology; Faculty of Medicine; Thammasat University; Pathum Thani; Thailand
3. Department of Medicine; Ramathibodi Hospital; Mahidol University; Bangkok; Thailand
4. Department of Biostatistics; Faculty of Medicine; Thammasat University; Pathum Thani; Thailand