Background: Postpartum haemorrhage (PPH) is the leading cause of maternal mortality. Uterotonics are the mainstay of PPH prevention. Objectives: To compare the efficacy of misoprostol and oxytocin for the prevention of PPH, and to evaluate the trustworthiness of trials comparing these uterotonics. Search strategy and selection criteria: Seven databases were searched for peer-reviewed literature, meeting the inclusion criteria of randomized controlled trials (RCTs) comparing misoprostol and oxytocin for the prevention of PPH. Data Collection and Analysis: Data were collected by two independent reviewers. Individual participant data (IPD) was meta-analyzed for outcomes PPH≥500mL and PPH≥1000mL. RCTs that did not share IPD were classified as trustworthy or not and were included in an aggregate data meta-analysis according to trustworthiness. Main results: Of 79 eligible RCTs, ten (12.7%) provided IPD, of which six were included. Analysis of IPD showed PPH≥500mL to be significantly higher in the misoprostol than the oxytocin group (2,022 women, aOR 1.84, 95% CI 1.43- 2.34). For PPH≥1000mL, analysis of IPD showed misoprostol and oxytocin were comparable (2022 women, OR 1.14, 95% CI 0.68- 1.91). Of the 69 studies that did not provide IPD, 23 (33.3%) were assessed as trustworthy. Analysis of trustworthy data (IPD and 23 aggregate data RCTs) showed no difference between misoprostol and oxytocin for PPH≥500mL (24,334 women, OR 1.01, 95% CI 0.69- 1.49), while misoprostol significantly increased the risk for PPH≥1000 (25,249 women, OR 1.36, 95% CI 1.16- 1.59). Conclusions: Of 79 RCTs comparing misoprostol and oxytocin for the prevention of PPH, 36.7% met trustworthiness criteria. Analysis of trustworthy data suggests oxytocin is superior to misoprostol for preventing PPH.

Background: Pregnancies complicated by placental insufficiency are characterised by increased oxidative stress. It has been suggested that melatonin has antioxidant properties and contributes to the maintenance of placental homeostasis. Objective: To systematically review the available literature about melatonin in pregnancies complicated by placental insufficiency, specifically preeclampsia and fetal growth restriction, exploring three different aspects: 1) maternal melatonin levels; 2) expression and activity of melatonin placental receptors; 3) effects of maternal melatonin administration. Search strategy: PubMed (Medline) and Scopus were searched until December 2020. Selection criteria: Published literature in English language describing the role of melatonin in pregnancies complicated by placental insufficiency, with a specific focus on preeclampsia and fetal growth restriction. Data collection and analysis: Identified studies were screened and assessed independently by two authors. Data were extracted and compiled in a qualitative evidence synthesis. Main results: Pregnancies complicated by placental insufficiency show a significant reduction in maternal systemic serum melatonin levels and a significant reduction in the expression of placental melatonin receptors. Melatonin administration in pregnancy seems safe and may reduce oxidative stress. Conclusion: The circadian pattern of melatonin secretion seems to be altered in pregnancies complicated by placental insufficiency. This is reflected by lower production of melatonin, with consequent lower systemic and placental concentrations, and lower expression of melatonin receptors, thus reducing the local release of the indole and its autocrine function. Funding: None Keywords: Melatonin, Preeclampsia, Fetal growth restriction, Placental insufficiency, Review.