ImportanceSome young people who identify as transgender and seek gender-affirming medical care subsequently reidentify with their sex registered at birth. Evidence regarding the frequency and characteristics of this experience is lacking.ObjectiveTo determine the frequency of reidentification and explore associated characteristics in a pediatric gender clinic setting.Design, Setting, and ParticipantsThis retrospective cohort study examined all referrals to the Child and Adolescent Health Service Gender Diversity Service at Perth Children’s Hospital between January 1, 2014, and December 31, 2020. The Gender Diversity Service is the sole statewide specialist service in Western Australia that provides children and adolescents up to age 18 years with multidisciplinary assessment, information, support, and gender-affirming medical care. All closed referrals for this study were audited between May 1, 2021, and August 8, 2022.ExposureReidentification with birth-registered sex.Main Outcomes and MeasuresThe number of referrals closed due to reported reidentification with birth-registered sex was determined, as well as descriptives and frequencies of patient demographics (age, birth-registered sex), informant source, International Statistical Classification of Diseases, Tenth Revision gender-related diagnoses, pubertal status, any gender-affirming medical treatment received, and whether subsequent re-referrals were received.ResultsOf 552 closed referrals during the study period, a reason for closure could be determined for 548 patients, including 211 birth-registered males (mean [SD] age, 13.88 [2.00] years) and 337 birth-registered females (mean [SD] age, 15.81 [2.22] years). Patients who reidentified with their birth-registered sex comprised 5.3% (29 of 548; 95% CI, 3.6%-7.5%) of all referral closures. Except for 2 patients, reidentification occurred before or during early stages of assessment (93.1%; 95% CI, 77.2%-99.2%). Two patients who reidentified with their birth-registered sex did so following initiation of puberty suppression or gender-affirming hormone treatment (1.0% of 196 patients who initiated any gender-affirming medical treatment; 95% CI, 0.1%-3.6%).Conclusions and RelevanceThese findings from a pediatric gender clinic audit indicate that a small proportion of patients, and a very small proportion of those who initiated medical gender-affirming treatment, reidentified with their birth-registered sex during the study period. Longitudinal follow-up studies, including qualitative self-report, are required to understand different pathways of gender identity experience.