Author Contributions: Dr Wachman 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: Wachman, Hayes, Brown, Paul, Huggins, Aranda, Davis.
Acquisition of data: Wachman, Hayes, Brown, Harvey-Wilkes.
Analysis and interpretation of data: Wachman, Hayes, Brown, Harvey-Wilkes, Terrin, Huggins, Aranda, Davis.
Drafting of the manuscript: Wachman, Hayes, Terrin, Huggins, Aranda, Davis.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Wachman, Terrin.
Obtained funding: Wachman, Hayes, Davis.
Administrative, technical, or material support: Hayes, Brown, Paul, Harvey-Wilkes, Aranda, Davis.
Study supervision: Hayes, Brown, Harvey-Wilkes, Huggins, Davis.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Davis reported receiving payment for lectures at Winchester Hospital and the Medical University of South Carolina. No other disclosures were reported.
Funding/Support: This study was supported in part by National Institutes of Health (NIH) funding of data collection, single-nucleotide polymorphism genotyping, and data analyses (DA024806-01A2 to Dr Hayes and R01DA032889-01A1 to Dr Davis); the Tufts Medical Center's Natalie Zucker and Susan Saltonstall Grants to Dr Wachman, which supported laboratory analyses; National Research Service Award T32HD055163 from the Eunice Kennedy Shriver National Institute of Child Health to Dr Paul, which supported graduate education and training; and a National Center for Advancing Translational Sciences NIH grant UL1 TR000073 through the Tufts Clinical and Translational Science Institute to Drs Terrin and Davis.
Role of the Sponsors: The funding organizations did not participate in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Additional Contributions: We thank the medical and nursing staff of labor and delivery, mother-infant units, and neonatal units of Tufts Medical Center, Melrose Wakefield Hospital, Brockton Hospital, Lowell General Hospital, and Eastern Maine Medical Center; and Ozlem Kasaroglu, MD, Mario Cordova, MD, and Teresa Marino, MD, from Tufts Medical Center, Hira Shrestha, BA, from Eastern Maine Medical Center, and Nicole Heller, MA, Beth Logan, PhD, and Deborah Morrison, MA, from the University of Maine for their assistance with enrollment and data collection. Ms Morrison was compensated through grant support as a study coordinator.