Prenatal diagnosis of Prader–Willi syndrome via maternal UPD15 with placental mosaicism: incidental discovery of fetal DMD carrier status

When NIPT suggests a high risk of T15, clinicians should maintain a high suspicion for the "trisomy rescue" mechanism, where an initially trisomic zygote undergoes mitotic correction, ultimately forming UPD15 with CPM. The potential discordance between NIPT and the actual fetal genetic status necessitates definitive prenatal diagnosis, which has critical implications for subsequent pregnancy management. Therefore, the concomitant findings of PWS and DMD carrier status require comprehensive prognostic evaluation and recurrence risk assessment.