Received March 23, 2023
Accepted September 30, 2023

Hydatidiform mole and coexisting fetus is a very rare disease of which etiology is still inconclusive. This disease can also occur after assisted reproduction, often leading to the death of normal embryos and other serious complications. We report a case of partial hydatidiform mole and coexisting fetus after frozen embryo transplantation. More than 2 months after the patient underwent transplantation of 2 blastocysts (scored 4AB and 4BC), B-ultrasound showed a single live intrauterine fetus with a large dense dotted strong echo area. The patient was treated with chemotherapy after the termination of pregnancy due to persistently increased human chorionic gonadotropin. Many studies have confirmed that the predictive value of trophoblast quality for pregnancy prognosis might be high. In the context of this case, in addition to the possibility of partial hydatidiform mole caused by multiple sperm entering the egg, we also speculate that it may be related to the poor quality of the trophoblastic ectoderm of the transferred embryo. In the process of assisted reproduction, reluctant transfer of embryos with poor trophoblastic ectoderm level in multiple embryo transfer may adversely affect the pregnancy outcome.