The girl was born earlier this month at Assuta Medical Center in Ashdod, the hospital said on Tuesday.
Fetus-to-fetus cases occur only about once in 500,000 births.
Checks and ultrasounds in the later stages of pregnancy had already identified that the girl’s stomach was enlarged, and after her natural delivery, the doctors carefully examined her and confirmed that there was something to the interior of the newborn.
She immediately underwent a battery of additional examinations, including ultrasound and an x-ray.
“We were surprised to find out that it was an embryo,” said Omer Globus, director of neonatology at Assuta.
A team of top medical center experts performed the operation, ultimately removing two similar bags from the girl’s stomach.
“We think there was more than one there, and we’re still checking it out,” he said.
Globus pointed out that the remains were not a fully formed embryo, but rather an embryo that only partially developed. Doctors were able to see bones and a heart, he said.
“But it didn’t look like an embryo like you might imagine,” he said.
The operation was successful and the girl is expected to make a full recovery, Globus said. The girl and her mother, who has three other children, have already been sent home.
Globus said there are a number of theories as to how such cases occur, one being that pregnancy begins with twins, but one embryo is then absorbed into the other.
“This happens as part of the process of fetal development when there are cavities that close during development and one of the embryos enters such a space,” he said. “The fetus inside is partially developing but not living and staying there. ”