A highly unusual medical case has emerged from Buldhana district in Maharashtra, where doctors discovered a rare condition known as “foetus in fetu” in a 35-year-old pregnant woman. This medical state, which occurs in approximately 1 in 500,000 live births, involves a malformed fetus developing inside the body of its twin.
The news became public when the woman, who was eight months pregnant, visited the district hospital for a routine check-up. During a sonography test, the medical staff were shocked to find a fetal mass inside the unborn baby. This condition, recognised in medical terms as the foetus in fetu, is considered one of the rarest congenital conditions. Keep reading as we understand it closely.
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What is Fetus in Fetu?
Foetus in fetu (FIF) is a rare congenital anomaly where a malformed parasitic twin develops inside the body of its normally developed twin, essentially forming a “foetus in within a fetu”—usually appearing as an abdominal mass in the affected infant. This condition is believed to occur when identical twins fail to separate properly in the early stages of fetal development. As a result, one twin becomes enclosed within the body of the other.
Theories behind its origin
The exact cause of foetus in fetu remains uncertain, but two primary theories seek to explain its occurrence:
Parasitic Twin Hypothesis: This theory suggests that foetus in fetu arises when an underdeveloped parasitic twin forms within the host twin’s body during early gestation. The parasitic twin is entirely dependent on the host twin for survival and does not develop independently.
Teratoma Hypothesis: Another perspective suggests that foetus in fetu is a highly developed form of teratoma—a type of tumour containing different tissue types. Unlike teratomas, however, foetus in fetu exhibits structural organisation, such as a vertebral column and organ arrangement along a central axis.
How is it diagnosed and treated?
This condition is typically detected in babyhood when a growing mass in the abdomen raises concerns. However, in rare cases like the one in Maharashtra, it can remain undetected until advanced pregnancy. Imaging techniques such as ultrasound, CT scans, and MRIs are used to confirm the diagnosis.
According to the National Institute of Health (NIH), the primary treatment for FIF is surgical removal of the parasitic twin. Since it lacks an independent circulatory system, it cannot survive outside the host body. Complete excision is usually curative, and post-surgical outcomes are generally positive.
