Fetus in fetu: the importance of autopsy in uncovering hidden abnormalities

Fetus in fetu (FIF) is a rare anomaly of embryogenesis in which a malformed parasitic twin is found within the body of the normally developed host twin. It has a reported incidence of 1 per 500 000 births with a 2:1 male predominance. The authors present a unique case of FIF, where autopsy investigation played a pivotal role in identifying this exceptionally rare anomaly, rarely documented in the literature. A primigravida woman in her early 20s was diagnosed with FIF at 13+3 weeks of gestation. She opted for medical termination of her pregnancy. The postmortem examination confirmed the diagnosis of FIF. Malformations in both fetuses, namely, partial urorectal septum malformation in the parasitic twin and heterotaxy syndrome in the host twin, were unmasked by fetal autopsy.The significance of autopsy examination in FIF cases is underscored by our case, as it facilitates the diagnosis of this rare entity and the reporting of congenital anomalies in the aforementioned.