Parasitic fetus, also known as Fetus in Fetu, as the name suggests, is a twin embryo that is encapsulated in another embryo early in its development (usually 24-48 hours after fertilization of the egg), and when the encapsulated embryo develops and gives birth, the encapsulated embryo exists in the fetus after delivery and grows along with the baby, sucking up the baby’s nutrients, and develops abnormally. Parasitism is a rare embryonic developmental abnormality with a publication rate of about 1 in 500,000-1 million. Since it was first reported in the mid-19th century, there are currently about 100 cases reported worldwide. Preoperatively, parasitic fetuses need to be differentiated from teratomas and neuroblastomas. Intraoperative complete excision of teratomas is an important means to prevent recurrence or malignancy. In recent years, two cases of parasitized fetus were admitted to the Department of Pediatric Surgery of West China Hospital of Sichuan University and were discharged from the hospital after surgical treatment. The experience of these two cases of parasitized fetus has been published in the British journal BMC Pediatrics.