1. Department of Maternal and Child Health, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
2. Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina.
3. Department of Maternal, Fetal Medicine, School of Medicine, University of North Carolina, Chapel Hill, North Carolina.
4. Slone Epidemiology Center, Boston University, Boston, Massachusetts.
5. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.