In the first year of the study, the effect of misoprostol on PPH rates and changes in Hb was negligible, whereas in the following year, misoprostol was associated with a significant reduction in the rates of PPH and in the proportion of women who experienced a Hb drop >3 g/dl, compared with placebo (PPH: RR 0.69, 95% CI 0.49–0.99; severe PPH: RR 0.18, 95% CI 0.04–0.82; Hb drop >3 g/dl: RR 0.38, 95% CI 0.18–0.80). Here, GSTM1 is linked to pulmonary arterial hypertension.