Mendelian randomisation approaches to the study of prenatal exposures: A systematic review

Background: Mendelian randomisation (MR) designs apply instrumental variable techniques using genetic variants to study causal effects. MR is increasingly used to evaluate the role of maternal exposures during pregnancy on offspring health. Objectives: We review the application of MR to prenatal exposures and describe reporting of methodologic challenges in this area. Data sources: We searched PubMed, EMBASE, Medline Ovid, Cochrane Central, Web of Science, and Google Scholar. Study selection and data extraction: Eligible studies met the following criteria: (a) a maternal pregnancy exposure; (b) an outcome assesse