1. Department of Pediatrics Yokohama City University Hospital
2. Japan Breastfeeding Association
3. Department of Obstetrics and Gynecology Japanese Red Cross Medical Center
4. Department of Pediatrics Saiseikai Hyogo‐ken Hospital
5. Department of Pediatrics Osaka City Juso Hospital
6. Department of Obstetrics and Gynecology Toyama Prefectural Central Hospital