OBJECTIVETo assess natural history of otitis media with effusion (OME)-related hearing loss and OME causing hearing loss in children under 12 years.METHODSEmbase, MEDLINE, CINAHL, INAHTA database, CENTRAL, CDSR, Epistemonikos and PsycINFO were searched to identify observational single group studies, and comparative studies with untreated control arms published in English up to June 2022, reporting natural history of OME-related hearing loss and OME causing hearing loss. Risk of bias and overall quality of evidence were assessed using the JBI (Joanna Briggs Institute (JBI) checklist and GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology, respectively.RESULTSThirteen studies with 24-639 children were included. Resolution of OME-related hearing loss was 50% by 3 months, 60% by 6 months and 61-77% by 12 months. Resolution of OME causing hearing loss (OME of <1 month, >3 months, >6 months or unknown duration before follow-up) was 23-55% by 3 months, 20-50% by 6 months, 31% by 9 months and 21-93% by 12 months, depending on population and how resolution was defined. Resolution of chronic OME (OME of >12 months duration before follow-up) was only 7% by 1 month, 12% by 6 months and 6% by 12 months. Resolution was only 42% by 57 months in children with primary ciliary dyskinesia.CONCLUSIONSThere was greater resolution of OME-related hearing loss over longer follow-up periods. Resolution of OME causing hearing loss also showed a trend towards greater resolution over longer follow-up periods; however, this did not follow a linear pattern, potentially due to differences in populations and definitions of resolution across studies.