Complete hydatidiform mole in one twin after embryo transfer: a case report and literature review.

A complete hydatidiform mole coexisting with a normal fetus in a twin gestation (CHMCF) is an extremely rare form of abnormal multifetal gestation characterized by the coexistence of a normal fetus and its placenta alongside a complete hydatidiform mole, with a markedly increased risk of persistent gestational trophoblastic disease (PTD) in the mother. Embryo transfer, as a key procedure in assisted reproductive technology, achieves conception by transferring in vitro-fertilized embryos into the uterine cavity. Although it addresses infertility, it may also present distinct clinical scenarios involving rare gestational complications. This report describes a case of a complete hydatidiform mole coexisting with a fetus in a twin gestation after embryo transfer. By integrating serial changes in serum β-human chorionic gonadotropin (β-hCG) levels, ultrasonographic features, chromosomal analysis, and histopathological findings, we summarize the diagnostic and management course and review the relevant literature.