However, observations are not always charted correctly, and appropriate and timely clinical responses to abnormal physiology do not always occur.1, 4, 6 Poor chart design may contribute to such failures.7, 8, 9 In 2007, the United Kingdom (UK) Confidential Enquiry into Maternal and Child Health (CEMACH) proposed that a single maternal observation chart should be used for all obstetric admissions in all settings.4 At the time, the ‘CEMACH’ chart was no more than an example of good practice, being neither evidence-based nor validated. It has not been universally used in UK midwifery or obstetric units.10, 11 Recently, researchers in Australia have used an evidence-based approach, and an emphasis on ‘human factors’ and user experience, to design improved, ‘standardised’ vital signs charts for general patient use.8, 9, 12, 13, 14, 15During an analysis of paper vital sign charts in consultant-led UK maternity units,3 design errors were commonly noted. Therefore, we decided to investigate this by focusing on common design faults that might hamper the charts’ safe and successful use.