1. Division of Maternal and Fetal Medicine, Department of Obstetrics and Gynecology, Duke University School of Medicine, Durham, North Carolina, USA.
2. Diaper Bank of North Carolina, Durham, North Carolina, USA.
3. Department of Biostatistics and Bioinformatics, Duke University School of Medicine, Durham, North Carolina, USA.
4. Department of Family Medicine and Community Health, Duke University School of Medicine, Durham, North Carolina, USA.
5. Department of Population Health Sciences, Duke University School of Medicine, Durham, North Carolina, USA.