Funding for this research was provided by:
a Grant-in-Aid for the National Center for Child Health and Development from the Ministry of Health, Labour and Welfare (27-12)
Received: 16 January 2019
Accepted: 30 July 2019
First Online: 20 August 2019
Ethics approval and consent to participate
: Our study protocol was approved by the Human Ethics Committees of the children’s hospitals: the National Center for Child Health and Development (1460), Miyagi Children’s Hospital (MiyaKoRinriDai327); and Saitama Children’s Medical Center (2016–06-006).
: Not applicable. Patient information was handled anonymously at each institution, and the opportunity to withdraw participation was provided to all participants and their guardians by posting flyers around the hospital.
: All authors declare that they have no competing interests.