Abstract Background Cannabis use during pregnancy has been increasing and is associated with adverse neonatal outcomes, such as low birth weight (LBW) and preterm birth (PTB). It remains largely unknown whether the association between cannabis use in pregnancy and increased risk of adverse neonatal outcomes is impacted by the frequency of cannabis use and whether thresholds exist below which risk is not significantly increased. The objective of this systematic review is to assess whether the association between cannabis use during pregnancy and the risk of adverse neonatal outcomes is dependent on the frequency of use and whether risk thresholds exist. Methods For this systematic review...