Main findings
Eighty COS studies have been registered covering a wide range of clinical issues in women’s and neonatal health. Only a minority (30%) had published a protocol and of these only 17% were assessed to meet all COS-STAP criteria. Twenty COS have been completed; only four and three met the COS-STAD and COST-STAR recommendations respectively. Studies where criteria were not met were primarily due to variation in patient engagement, outcome selection and the Delphi process.