Accepted for Publication: October 29, 2013.
Published Online: February 24, 2014. doi:10.1001/jamapediatrics.2013.4914.
Study concept and design: Liew, Olsen.
Acquisition of data: Liew, Olsen.
Analysis and interpretation of data: All authors.
Drafting of the manuscript: Liew, Ritz, Olsen.
Critical revision of the manuscript for important intellectual content: Liew, Rebordosa, Lee, Olsen.
Statistical analysis: Liew, Rebordosa, Lee.
Obtained funding: Olsen.
Administrative, technical, and material support: Liew, Olsen.
Study supervision: Ritz, Olsen.
Conflict of Interest Disclosures: Dr Rebordosa contributed to the study when she was at University of Arizona, and she currently works at Global Clinical Epidemiology, Drug Safety, and Epidemiology, Novartis Farmaceutica SA, Barcelona, Spain. No other disclosures were reported.
Funding/Support: This work was supported by the Danish Medical Research Council (grant 09-069178).
Role of the Sponsor: The Danish Medical Research Council had no role in the design and conduct of the study; collection, management, analysis, or interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: We thank Inge Eisensee, Humanistiks Datalogi, and Lone Fredslund, MA (Danish Epidemiology Science Centre, University of Aarhus) for data set preparation; Elani Streja, PhD (University of California, Los Angeles) for her support in SAS programming; and all physicians, nurses, interviewers, and mothers who participated in the study. None of the named contributors received compensation for their work on this study.