Published Online: July 8, 2013. doi:10.1001/jamapediatrics.2013.95.
Study concept and design: Bernard.
Acquisition of data: All authors.
Analysis and interpretation of data: All authors.
Drafting of the manuscript: Bernard.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: All authors.
Obtained funding: All authors.
Administrative, technical, and material support: All authors.
Study supervision: Bernard.
Conflict of Interest Disclosures: None reported.
Correction: This article was corrected online September 2, 2013, for a typographical error in the Methods section.