BACKGROUND: Risk factors for the placental disorders of pregnancy (pre-eclampsia, fetal growth restriction, preterm birth, and stillbirth) are complex, frequently involving the interplay between clinical factors and wider social and environmental determinants of health. Biomarkers modulate the maternal and fetal responses to biological processes that underlie the development of placental disorders. OBJECTIVES: To develop a standardised methodology to assess the importance of, and inter-relationships between, candidate risk factors for the various placental disorders. SEARCH STRATEGY: Systematic searches were conducted using Medline, Embase, Health Technology Assessments, Database of Abstracts of Reviews of Effects, Cochrane Library databases, Google Scholar, and reference lists of retrieved papers. SELECTION CRITERIA: We deployed a hierarchy of reviews, systematic reviews, and cohort studies with at least 1000 participants (100 for biomarker studies), published in the prior decade. DATA COLLECTION AND ANALYSIS: We assessed the strengths of association and quality of evidence linking risk factors with individual placental outcomes. CONCLUSIONS: We have developed a standardised approach to assess the importance and inter-relatedness of putative risk factors for the placental disorders of pregnancy.