Author Contributions: Dr Keren had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Keren, Zaoutis, Bridges, Herrera, Watson, Wheeler, Coffin.
Acquisition of data: Keren, Wheeler, Luan, Coffin.
Analysis and interpretation of data: Keren, Zaoutis, Bridges, Herrera, Licht, Luan, Coffin.
Drafting of the manuscript: Keren, Zaoutis, Bridges, Wheeler, Coffin.
Critical revision of the manuscript for important intellectual content: Keren, Zaoutis, Bridges, Herrera, Watson, Licht, Luan, Coffin.
Statistical analysis: Keren, Zaoutis, Luan, Coffin.
Obtained funding: Keren, Bridges, Herrera, Watson, Coffin.
Administrative, technical, or material support: Keren, Zaoutis, Bridges, Herrera, Watson, Wheeler, Licht, Coffin.
Study supervision: Keren, Zaoutis, Watson, Coffin.
Financial Disclosures: None reported.
Funding/Support: This work was supported by grant H23/CCH32253-02 from the Centers for Disease Control and Prevention (CDC). Dr Keren was supported by grant K23 HD043179 from the National Institute of Child Health and Human Development, Bethesda, Md.
Role of the Sponsors: Drs Bridges and Herrera, investigators from the CDC, were involved in the design of the study; the analysis and interpretation of the data; and the preparation, review, and approval of the manuscript. The National Institute of Child Health and Human Development did not have any involvement in the study.
Acknowledgment: We thank Russell Localia, PhD, JD, for his helpful voluntary comments on the statistical analysis, and Melissa Donovan, BA, for her paid assistance with abstracting data from medical records and chart review. We also thank Joseph Zorc, MD, Robert Grundmeier, MD, and Peter Pavlo, BS, for their assistance in electronic data acquisition, and Chris Feudtner, MD, PhD, MPH, for his comments on earlier drafts of the manuscript.