Received: 23 January 2020
Accepted: 10 June 2020
First Online: 16 July 2020
Ethics approval and consent to participate
: Ethical approval for this study was obtained from the Norwegian Data Inspectorate, the Regional Research Ethics Committee for Western Norway, and the Institutional Review Board of the US National Institute of Environmental Health Sciences, National Institutes of Health. Parents gave consent to data and sample collection, and all data were anonymized after collection.
: Not applicable.
: The authors declare no competing interests.