A randomised trial of a contraceptive vaginal ring in women at risk of HIV infection in Rwanda: Safety of intermittent and continuous use by Kestelyn, E, Agaba, S, Van Nuil, J, Uwineza, M, Umulisa, M, Mwambarangwe, L, Ndagijimana, J, De Baetselier, I, Buyze, J, Delvaux, T, Crucitti, T, Jespers, V, van de Wijgert, J