Maternal characteristics and causes associated with refractory postpartum haemorrhage after vaginal birth: a secondary analysis of the WHO CHAMPION trial data. - Widmer, M; Piaggio, G; Hofmeyr, GJ; Carroli, G; Coomarasamy, A; Gallos, I; Goudar, S; Gülmezoglu, AM; Lin, SL; Lumbiganon, P; Mugerwa, K; Owa, O; et al. (BJOG: An International Journal of Obstetrics & Gynaecology, 2020)