A mother in Israel received a shock when she was informed by doctors that her newborn baby had a 'twin' fetus inside her stomach.
The Times of Israel reports that doctors from Assuta Medical Center in Ashdod, Israel, first realized there could be a problem with the baby when they performed a late-pregnancy ultrasound on the mother.
Here, they saw that the baby's stomach was larger than it should be.
When the baby girl was born, doctors performed a series of tests, including ultrasounds and X-rays, where they spotted a partially developed fetus inside the baby's abdomen.
They then performed an operation to remove the fetus.
Live Science states that the phenomenon is known as 'fetus in fetu' (FIF) - where a developmentally abnormal fetus is found inside the body of its otherwise healthy twin.
A 2010 report, which was published in the Journal of Surgical Technique and Case Report, states that it is an extremely rare condition, occurring in about 1 in 500,000 births.
While it is not exactly clear on what causes the abnormal condition, scientists believe that the fetus is a a rare type of "parasitic twin," according to Arizona State University.
A parasitic twin forms during an identical-twin pregnancy when one of the fetuses is absorbed by the other.
Dr. Omer Globus, director of neonatology at Assuta Medical Center, told The Times of Israel: "It happens as part of the fetal development process when there are cavities that close during development and one of the embryos enters such a space.
"The fetus inside partially develops but does not live and remains there."
Another theory suggests that FIF is a type of teratoma, a tumor that can contain all three of the major cell types that are found in an early-stage human embryo.
According to the 2010 paper, researchers say that the presence of a spinal column distinguishes a diagnosis of FIF from a teratoma, as the latter does not have a spine.
The baby girl, who has not been identified, is said to be recovering well from her serious operation to remove the fetus from her stomach and is now at home with her mother.
In October, doctors in India claimed that a baby girl was born with eight embryos inside her stomach.
Her parents reportedly took her to hospital with concerns that she had a tumour due to her abnormally swelled stomach.
Doctors transferred the girl to the Rani Children Hospital & Research Centre in the city of Ranchi following a CT scan which suggested she had a tumour.
However, it has since been confirmed that the baby had FIF.
A total of eight undeveloped embryos were found in the girl's stomach, which is believed to be the highest number ever found in a newborn.
The baby girl underwent an operation to remove the embryos and according to reports, she fully recovered from the procedure.
