Received: 29 October 2018
Accepted: 20 February 2019
First Online: 4 March 2019
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 that they have no competing interests.
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