METHODS IN CLINICAL PHARMACOLOGY Methodological quality of antimalarial randomized controlled trials during pregnancy and its impact on the risk of low birth weight Correspondence Dr Anick Bérard, Research Chair on Medications, Pregnancy and Lactation, Faculty of Pharmacy, University of Montreal and Director of Research Unit on Medications and Pregnancy, Research Center CHU Ste-Justine 3175, Côte-Sainte-Catherine, Montréal (Québec), H3T 1C5, poste 4363, Canada. Tel.: +1 (514) 345 4931; Fax: +1 (514) 343 6120; E-mail: anick.berard@umontreal.ca Received 8 December 2015; revised 28 April 2016; accepted 30 April 2016 Flory T. Muanda 1,2 and Anick Bérard 1,2 1 Faculty of PharmacyUniversity of Montreal, 2900 Édouard Montpetit, Montréal, Québec, Canada, H3T 1J4 and 2 Research Center, CHU Sainte-Justine, 3175, Côte-Sainte-Catherine, Montréal, Québec, Canada, H3T 1C5 Keywords meta-regression, randomized controlled trials, risk of bias AIM To describe biases in antimalarial randomized controlled trials (RCTs) during pregnancy and their influence on antimalarial drug efficacy to reduce the risk of low birth weight (LBW). METHODS RCT characteristics and results were retrieved from a previous systematic review on the efficacy of antimalarials. The Cochrane risk of bias assessment was used to investigate source of biases in each RCT. The quality of RCT reporting published after the introduction of the CONSORT statement in medical literature in 1996 were compared to those published before 1996. A meta- regression analysis was performed to examine the impact of bias on the efficacy of antimalarials to reduce LBW after controlling for the time period prior to 1996. RESULTS Twenty out of 25 RCTs (80%) had a high risk of bias. The proportion of RCTs having a low risk of bias was higher in manuscripts published after the introduction of CONSORT compared to those published before 1996 for sequence generation (P = 0.04) and allocation concealment (P = 0.04). Heterogeneity between RCTs was associated with an overestimation of the efficacy of antimalarial drugs in reducing LBW in RCTs with inadequate methods for randomization, allocation concealment or not being free of other bias. CONCLUSION Antimalarial RCTs during pregnancy are poorly reported but may be improved by using the CONSORT statement. After taking into account the time period before 1996, we found that biases had an impact on the efficacy of antimalarials to reduce the risk of LBW. British Journal of Clinical Pharmacology Br J Clin Pharmacol (2016) 82 806–813 806 © 2016 The British Pharmacological Society DOI:10.1111/bcp.12998