Fetus-in-fetu (FIF), which is hard to believe, is referred to as “anomaly” (an abnormal, abnormal) in medicine, and 200 cases have been reported worldwide who have experienced this condition.
While this syndrome can sometimes be detected during the mother’s pregnancy, it mostly occurs in newborns and is seen in approximately 1 in 500,000 births. It is much less common in adults than in newborns. Let’s take a closer look at why and how this phenomenon occurs.
In fact, it all starts during the first development of the fertilized egg.
During fertilization, when the cell clusters that make up the embryo develop normally, healthy twins are formed, while if the two embryos are of different sizes, the larger one receives enough placental blood and continues to develop to become a normal fetus. The small one, on the other hand, cannot develop due to unfavorable intra-uterine conditions and dies and remains lifeless in that area.
Researchers working on how this symptom occurs are united in two common theories.
According to one view, the fetus’s organs, including the heart, brain, pupils, intestines, or different limbs, differentiate, while in another case, normal twins deform into symmetrical conjoined twins.
Meecker first described FIF in the 19th century as the rare condition in which a fetus composed of deformed twins exists in the abdominal cavity of its healthy partner.
During the examination, the abdomen of the fetus showing this syndrome was swollen and soft at the same time, and the masses in the abdomen were clearly palpable. The mass had fetal appearance, limb-like structures, and abnormal skeletal and intestinal development.
In about 80% of cases, this abnormal condition occurs in the posterior region of the abdomen of the normal fetus, but it can also be seen in other parts of the body such as the chest, groin, and coccyx.
Most of the time, there is only one fetus inside the fetus, but there may be cases where two or more are present together.
For diagnosis and treatment, this mass, which causes the formation of a new fetus within the fetus, should be surgically removed and examined as it potentially damages the bodies of newborn babies.
Fetus-within-a-fetus syndrome may sometimes go undetected early in pregnancy.
While pregnancies last an average of 38-40 weeks, a mass was detected at the 25th week of a mother’s pregnancy and these masses increased as the pregnancy progressed. When these masses detected by ultrasound and MR were examined, it was understood that the formations would result in a fetus within a fetus.
In some cases, in babies born in a healthy way, a twin may be detected as a mass in the abdomen in the following years.
In the samples seen after birth, this situation mostly occurs around the age of 1, while the existing mass enlarges and presses on the surrounding tissues, and as a result of the complaints created by this pressure, it is revealed that the baby carries the remains of his sibling within himself.
In an Indian woman who had different cognitive problems such as reading and listening, remnants of her brother were found in her brain years after her birth.
When it was understood that the young woman, who was unaware of the remains she had, had this syndrome, the masses belonging to her twin sister, who had tortured her for 26 years, were removed with an unusual surgical technique.
From time to time, it is possible to confuse FIF with tumors that develop in other ways and for different reasons.
The diagnosis of “teratoma”, which is a type of tumor as well as masses that cause a fetus within the fetus, is very difficult to diagnose, and masses that cause fetus formation can often be mistaken for teratoma.
In the past, scientists thought that the fetus in the fetus was the result of a highly developed teratoma rather than the product of an abnormal development.
Teratomas are the most common malignant tumors in infants, which can include hair, teeth, bone and organ tissues, which are composed of tissues foreign to the region of the body.
Teratoma is usually found in the ovaries, testicles, peritoneum, and coccyx, while FIF is located in the amniotic sac, which can stop growing due to insufficient blood flow. In addition, cysts that cause a fetus within a fetus are benign and have a clean blood supply similar to the structure of the umbilical cord.
- Sources: Prof. Dr. Cansun Demir, Live Science, Popular Science, The Embryo Project Encyclopedia, Frontiers, Cureus
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