[1] Univ Pretoria, Kalafong Hosp, Dept Paediat, Pretoria, South Africa
[2] South Africa Med Res Council, Hlth Syst Res Unit, Cape Town, South Africa
[3] South Africa Med Res Council, Biostatist Unit, Cape Town, South Africa
[4] Univ Pretoria, Res Ctr Maternal Fetal, Newborn & Child Hlth Care Strategies, Pretoria, South Africa
[5] South African Med Res Council, Maternal & Infant Hlth Care Strategies Res Unit, Pretoria, South Africa
[6] Gauteng Dept Hlth, Tshwane Dist Hlth Serv, Johannesburg, South Africa