Objective: To identify which risk communication graphics are easiest to understand when communicating risks surrounding birth; and investigate the effect of numeracy and health literacy on understanding. Design: Online survey with randomised content Setting: UK Population: Women and their partners, healthcare professionals and stakeholders in the UK. Methods: Seven candidate graphics (’10-person’, ‘100-person’, ’10-circle’, ‘100-circle’ icon arrays, ‘bar charts’, ‘pie charts’ and ‘words’) were co-produced with a patient and public involvement group. These were used to develop seven online surveys. Participants were recruited using social media and adverts in participating hospitals. Each participant was randomised to see one of seven surveys, the survey questions remained the same, the graphics varied. Data were collected on risk perception, perceived ease of understanding and preference, alongside demographic factors, numeracy skills and health literacy. Main outcome measures: Objective comprehension and subjective preference for graphics. Results: There were 858 participants, 771 women/partners/parents and 87 healthcare professionals and stakeholders. 70% of participants answered all four numeracy questions correctly, and respondents reported high health literacy (76.5% can understand health material, 72.8% were comfortable completing medical forms). All graphics were understood; however, the ‘100-person’ icon array elicited the best score when comparing two risks (mean score 97.5% compared to next best performing graphic 95.8%), 41% believed it was the easiest to understand and 36% selected it as the preferred graphic. Conclusions: All graphics are well understood. The ‘100-person’ icon array scored best in terms of risk comparison and participant preference. Using this graphic may support high-quality communication of risk in maternity care.