Fetus in fetu: a twin riddle

• A 32-year-old pregnant woman in Maharashtra was diagnosed with a rare case of “foetus in fetu” during a sonographic assessment.

• This condition occurs when a malformed foetus develops inside another in a monozygotic twin pregnancy.

• The condition is a rare congenital anomaly that affects about one in 500,000 births, with less than 200 cases reported worldwide.

• The cause is believed to result from an anomaly during the development of monozygotic or identical twins.

• The smaller twin gets trapped within the larger twin, resulting in a “parasitic” twin that draws its blood supply and nutrients from the other “host” twin.

• The parasitic twin affects the host twin’s health and may compress vital organs in the host.

• Treatment involves surgical excision of the parasitic twin, with special attention given to the foetus’ blood supply.

• The exact mechanism of how one twin becomes enclosed within the other is not fully understood, making diagnosis challenging.