International Centre for Reproductive Health, Ghent University, C. Heymanslaan 10, 9000 Ghent, Belgium; The South African Department of Science and Technology-National Research Foundation (DST-NRF) Centre of Excellence in Epidemiological Modelling and Analysis (SACEMA), Stellenbosch University, Matieland, Stellenbosch 7602, South Africa; Center for Statistics, Hasselt University, Martelarenlaan 42, 3500 Hasselt, Belgium; Rega Institute for Medical Research, KU Leuven, Herestraat 49, 3000 Leuven, Belgium; Department of Global Health Faculty of Medicine and Health Sciences, Stellenbosch University, Matieland, Stellenbosch 7602, South Africa.