Buzz
Since the beginning of life, birth anomalies have been a recurring phenomenon. Some of these anomalies are so peculiar and extraordinary that they verge on the bizarre and unsettling. Fetus in fetu is one such rare condition, where one twin is discovered inside the body of the other.
This condition has been inaccurately described as a baby being born “pregnant.” While the term is incorrect, the idea is somewhat close, as fetus in fetu involves one individual being entirely encapsulated within the developing body of another. Often, this condition goes unnoticed, resulting in a single birth where one individual harbors another within them. Below are ten astonishing facts about fetus in fetu, a rare anomaly where one person is born with another fully embedded inside them.
10. Parasitic Nature
Fetuses in fetu are essentially parasitic twins, where the absorbed twin acts as a parasite to the host twin. This distinguishes them from typical conjoined twins, as one twin exists entirely within the other. The extent to which the absorbed twin “lives” is a topic of debate, but as long as the cells remain alive, even in a basic form, the individual persists.
This is the only scenario where one human can be a parasite to another, aside from the debated case of unborn babies in the womb. The debate hinges on the fact that parasites typically drain resources from their host, reducing their fitness. However, unborn children often enhance the mother’s fitness in various ways.
9. Benign Nature
Although technically parasitic, the absorbed twin usually doesn’t harm the host, aside from the presence of fused body parts like a spine or limbs. These remnants of the absorbed twin often go unnoticed for years, causing no significant harm. Compared to other anomalies doctors might find, fetus in fetu, while alarming, is generally benign.
8. The Abdominal Location
In most instances of fetus in fetu, the parasitic twin is absorbed into the host’s abdomen, specifically the retroperitoneal cavity. Despite being the most common location, this anomaly can be missed during routine screenings by doctors, leading to surprising and unusual discoveries later in life. It’s crucial for medical professionals to examine the abdominal area, including the stomach, for any growths, such as a fetus in fetu, during the examination of a newborn baby.
7. Uncommon Locations
Occasionally, the absorbed fetus is found in areas other than the abdomen, though such cases are even rarer. In extraordinary instances, individuals have been born with remnants of a twin in their cranial cavity—meaning the mass of cells that would have been their twin is located inside their head.
Other rare locations include the mediastinum, which houses the heart and esophagus, and even the scrotum. Some individuals have been born with parts of a twin fused into their scrotum. While this may sound alarming, it is typically benign compared to other potential growths the body might develop.
6. Higher Prevalence in Males
Fetus in fetu occurrences are exceedingly rare overall, but they are even less common in females compared to males. Statistically, males are twice as likely to be born with another individual fused inside them.
In certain instances, when a fetus in fetu is located in the abdomen or scrotum, it can lead to complications and developmental issues with the testes of the host. For example, one case involved an infant born with scrotal swelling, which revealed the presence of a fetus. After a complete surgical removal, the child went on to live a normal, healthy life.
5. Exceptional Rarity
How rare are fetus in fetu cases? Exceptionally rare. To put it in perspective, monozygotic twins, or “identical twins,” occur in about one in every 333 births. Conjoined twins, an even rarer phenomenon, occur once in every 50,000 to 100,000 births. Fetus in fetu cases are even more uncommon, occurring once in every 500,000 births, with fewer than 100 documented cases worldwide. The likelihood of this condition affecting your child or being present in your body is incredibly slim.
4. Contents of the Absorbed Fetus
What exactly is found inside someone living with their absorbed sibling? In the rare cases of fetus in fetu, a variety of structures have been discovered. Vertebrae are the most common, but entire limbs, such as arms or legs, have also been identified. In some instances, fetal heads, hair, teeth, and even male genitalia have been found within the host’s body.
Thankfully, medical science can detect and remove these anomalies, sparing individuals the distress of carrying parts of another person. Sometimes, the mass forms a sphere of bones, hair, teeth, and other tissues, eerily resembling a fetus still in the womb.
3. Surgical Intervention
For individuals born with a twin inside them, particularly newborns who won’t recall the procedure or adults relieved after years of discomfort, surgery is the effective solution for removing the absorbed fetus. Following a preoperative diagnosis using radiological imaging, the remnants of the parasitic twin can typically be excised without complications. Surgery remains the sole remedy, as the fusion of the fetus with the host usually occurs long before modern medical intervention could be applied.
Despite its unsettling nature—the idea of carrying a mass of tissue that could have been a sibling—the success rate of such operations is remarkably high, especially compared to the more complex and risky separation of conjoined twins. Fetus in fetu, while bizarre and rare, is ultimately a benign condition, despite the psychological unease and graphic imagery it evokes in medical literature.
2. Discovery in Adulthood
In some cases, fetus in fetu goes undetected during prenatal screenings or at birth. Individuals may live their entire lives unaware they are carrying their would-be twin inside them—a chilling reality for the rare few affected. One patient, for instance, reached the age of 30 before a head and vertebral column were discovered in her abdomen. Upon removal, additional findings included teeth, hair, small limbs, and an umbilical cord.
Adult patients often misinterpret the presence of an absorbed fetus as swelling, or doctors may misdiagnose it as a tumor. In one case, a parasitic twin, initially thought to be a tumor, was connected to the host twin’s blood supply and hindered his breathing and comfort. After removal, the host twin experienced immediate relief, and all symptoms vanished. Such cases, though extraordinarily rare, highlight the condition’s complexity. Fewer than 15 instances of fetus in fetu have been identified in living adults.
1. Identification Methods
How is fetus in fetu detected? Most cases are identified prenatally through ultrasounds before birth. Radiography, including X-rays and similar technologies, is also effective in diagnosing the condition. Often, a combination of imaging techniques is used to determine the nature of any mass detected in an unborn child or infant.
In some instances, the baby is born with the absorbed fetus still undetected. The parasitic twin is only noticed when swelling appears in the affected area, prompting further examination. The majority of cases are identified shortly after birth, with 89 percent of fetus in fetu instances discovered before the host baby reaches 18 months of age.
