1. SAMRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, University of the Witwatersrand, Johannesburg, South Africa
2. Division of Epidemiology and Biostatistics, University of the Witwatersrand, South Africa
3. MRC Epidemiology Unit, University of Cambridge, Cambridge, United Kingdom
4. Research Initiative for Cities Health and Equity, University of Cape Town, Cape Town, South Africa
5. Institute for Developmental Science and Global Health Research Institute, University of Southampton, Southampton, UK