Funding for this research was provided by:
Ministry of the Environment, Government of Japan (NA)
Received: 23 March 2021
Accepted: 26 May 2021
First Online: 5 June 2021
: The study protocol was reviewed and approved by the institutional review board of the National Center for Child Health and Development (Number 1440). Electronic informed consent was obtained from all mothers.
: Not applicable
: None of the authors have any conflicts of interest.