At 24 h postpartum , primary PPH occurred in 163 ( 28.6 % ) participants in the misoprostol group and 99 ( 17.4 % ) participants in the oxytocin group ( relative risk [ RR ] 1.64 , 95 % CI 1.32 to 2.05 , p < 0.001 ; absolute risk difference 11.2 % , 95 % CI 6.44 to 16.1 ) .