1. Department of Obstetrics and GynecologyNihon University Hospital, 1‐6 Kanda Surugadai Chiyoda‐ku Tokyo Japan
2. Department of Obstetrics and GynecologyNihon University School of Medicine, 30‐1 Oyaguchi Kami‐cho, Itabashi‐ku Tokyo Japan
3. Department of Cardiovascular SurgeryNihon University Hospital, 1‐6 Kanda Surugadai Chiyoda‐ku Tokyo Japan
4. Department of Pathology and MicrobiologyNihon University School of Medicine, 30‐1 Oyaguchi Kami‐cho, Itabashi‐ku Tokyo Japan