Author’s response to reviews Title: MAGnesium sulphate for fetal neuroprotection to prevent Cerebral Palsy (MAG-CP) - Implementation of a national guideline in Canada Authors:

Required revisions:  The abstract includes a clear statement supporting the need for MgSO4 for women at risk of very preterm birth to reduce the likelihood of cerebral palsy in the child, a brief description of the study design, methods, KT strategies used, the primary outcome, key results and conclusions of this project.  Recommendations: (a). Include a statement describing the extent of the practice gap (e.g. baseline practice rates compared to optimal), Thank you. We have included baseline practice rates in the introduction, as well an estimate in the abstract. (line 83) (b). Explicitly identify this as an implementation study current wording used is 'managed KT intervention' which is not clear and needs to be defined in the body of the paper if used, and The title has been changed to emphasize that this is an implementation project. As per Reviewer #1, we have changed „managed KT‟ to „multifaceted KT‟ for clarity. (c) Describe secondary outcomes of interest as well. We have clarified that our secondary outcomes of interest were related to safety: maternal effects and effect on neonatal resuscitation. Background and supporting literature Required revisions:  The authors provided rationale and supporting literature for use of MgSO4 for women at risk of very preterm birth to reduce the likelihood of cerebral palsy in the child.  They described issues that were perceived to be barriers to uptake of this practice (e.g. concerns about potential effect of MgSO4 on FHR and increased neonatal resuscitation, lack of understanding of neuroprotective mechanism of action and inadequate studies describing long-term adverse pediatric outcomes other than CP).  The purpose of the study is clearly stated: "increase 'optimal' use of MgSO4 (i.e., MgSO4 use when and only when indicated) to 80% of eligible women over four years (2011-15), as well as document any maternal or fetal adverse effects".