In Reply Our Research Letter analyzed free-text entries for the optional ClinicalTrials.gov data element, Gender Eligibility Description, as provided by study sponsors and investigators during trial registration. Of 1573 trials initiated between 2017 and 2022, nearly two-thirds described eligibility criteria based on sex at birth while another 11% did not contain terms for either gender identity or sex at birth, indicating confusion about the concept of gender identity. Frequent conflation of terms for sex and gender in clinical research has been documented. For instance, one study found that the protocols and results publications for three-fourths of the sampled 128 randomized clinical trials in oncology included inconsistencies in sex and gender term usage.