Author Contributions: Dr Cnattingius 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: Villamor, Wikström, Granath, Cnattingius.
Acquisition of data: Cnattingius.
Analysis and interpretation of data: Cnattingius, Villamor, Johannson, Edstedt Bonamy, Persson, Wikström, Granath.
Drafting of the manuscript: Cnattingius, Villamor, Johannson, Edstedt Bonamy, Persson, Wikström, Granath.
Critical revision of the manuscript for important intellectual content: Villamor, Johansson, Edstedt Bonamy, Persson, Wikstrom, Granath.
Statistical analysis: Johansson, Cnattingius.
Obtained funding: Cnattingius.
Administrative, technical, or material support: Villamor, Edstedt Bonamy, Cnattingius.
Study supervision: Cnattingius.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Edstedt Bonamy reports receipt of an institutional grant or pending grant from the Swedish Research Council for Working Life and Social Health. The other authors report no disclosures.
Funding/Support: The study was funded by grants from Karolinska Institutet (Distinguished Professor Award to Dr Cnattingius).
Role of the Sponsor: The funder was not involved in the design and conduct of the study; collection, management, analysis, or interpretation of the data; and preparation, review, or approval of the manuscript, or decision to submit the manuscript for publication.
Acknowledgment: We thank Marian F. MacDorman, PhD, Division of Vital Statistics, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland, for providing information about preterm birth and infant mortality rates in the United States. Dr MacDorman did not receive any compensation for her work.