Effect of an intervention to promote contraceptive uptake on incident pregnancy: a randomized controlled trial among HIV positive couples in Zambia. - Wall, K.; Vwalika, B.; Haddad, L.; Htee Khu, N.; Vwalika, C.; Kilembe, W.; Chomba, E.; Stephenson, R.; Kleinbaum, D.; Nizam, A.; Brill, I.; Tichacek, A.; et al. (Retrovirology, 2012)