Shannon M. Clark, MD, FACOG on Instagram: "PMID: 33628563 Fetus in fetu (FIF) is an extremely rare developmental condition. It occurs in about 1 in 500 000 live births, and around 200 cases have been reported in medical literature. FIF is usually retroperitoneal, but it has been reported at various sites. Majority of cases have been described in neonates and children, and only few cases have been reported after the age of 15 years and most of them are male. Fetus in fetu occurs secondary to abno