1. Department of Maternal and Child Health, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA
2. Injury Prevention Research Center, University of North Carolina, Chapel Hill, North Carolina, USA
3. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA
4. Carolina Population Center, University of North Carolina, Chapel Hill, North Carolina, USA