Baldwin K, et al. - Researchers sought to discuss experience with routine evaluation for paternal germline mosaicism in a sperm donor population following a single report of an apparently de novo dominant disorder in a donor-conceived individual. An Adverse Outcome Report (AOR) had documentation of all reports of medical issues in fetuses or offspring conceived using donor semen at California Cryobank, and it was investigated to assess the etiology and risks to other offspring, the donor and his family. During the time period studied, they identified 13 donors with offspring with diagnoses of autosomal dominant (AD) disorders. Diagnosis of a de novo pathogenic variant for an autosomal dominant disorder in a donor-conceived individual, increases the risk of recurrence in other offspring in the event of gonadal mosaicism for a gamete donor than in the general population due to the greater-than-average number of potential offspring that may be conceived from one individual. Previously, the occurrence and diagnosis of the same AD disorder in two half-siblings from the same donor was accounted to identify mosaicism in a semen donor. In this study, while no evidence of gonadal mosaicism was identified for the cases investigated, they suggest performing routine evaluation of DNA from sperm cells to identify mosaicism and decrease the likelihood of recurrence, when possible.