1. Department of Pediatrics, Hokkaido University Hospital, Sapporo, Hokkaido 060-8648, Japan
2. Department of Pediatrics, National Defense Medical College, Tokorozawa 359-8513, Japan
3. Department of Cardiovascular and Thoracic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido 060-8648, Japan
4. Department of Obstetrics and Gynecology, Hokkaido University Hospital, Sapporo, Hokkaido 060-8648, Japan
5. Maternity and Perinatal Care Center, Hokkaido University Hospital, Sapporo 060-8648, Japan