Does magnesium sulfate increase the incidence of postpartum hemorrhage? A systematic review

The incidence of Postpartum Hemorrhage (PPH) is increasing in the western world. We hypothesize that magnesium sulfate (MgSO4) could be a contributing factor. MgSO4 might increase the incidence of PPH by induction of vasodilation, tocolytic effects, and effects on the blood like red cell deformity, platelet activity inhibition and a prolonged bleeding time. Based on these effects of MgSO4 a correlation with PPH is suspected. MgSO4 is widely used in the prevention of eclampsia. However, the working mechanism of this effective drug is largely unknown. We performed a systematic search to find all Randomized Controlled trials (RCTs) containing MgSO4 in preeclamsia as well as all MgSO4 studies with information on PPH. Titles, abstracts and references of publications were evaluated for appropriateness and whether they met the inclusion criteria. RCTs about MgSO4 with original data on PPH prevalence were included in our systematic review. We calculated the relative risk of PPH in every study as well as an overall relative risk. Four relevant and valid RCTs were found, totalling 11,621 relevant patients. The relative risk of PPH in women treated with MgSO4 is 0.964 (95% CI 0.886 1.050). In this systematic review we found no significant increase in PPH in women treated with MgSO4. However, there is still room for discussion due to the heterogeneity in methods (dosage and duration of treatment), results, and tertiary outcomes, as well as the small number of studies found with respect to this important issue.