A baby girl born in Israel this month is doing well after surgery to remove what is thought to be at least one embryo from her stomach, likely from a twin she absorbed. When the child's mother arrived at Ashdod's Assuta Medical Center to give birth, "we got the impression that the baby had a big tummy," Dr. Omer Globus, director of neonatology, tells the Jerusalem Post. "The moment the baby was born, we checked her and realized that we [could] feel something inside her stomach." What ultrasounds and an X-ray revealed was a fetus—possibly two. Such cases of "fetus in fetu" are extremely rare, thought to occur once in every 500,000 births, reports the Times of Israel. Doctors removed two sacs from the girl's stomach. Globus says the remains included at least one partially developed fetus with bones and a heart.
"It did not look like an embryo as you imagine it," Globus tells the Times. "We think that there was more than one there, and we are still checking that." The pregnancy might have begun as twins or triplets, with one embryo eventually absorbing the other(s). "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," says Globus. The other theory is that it's a benign type of tumor called a teratoma, which "can contain all three of the major cell types that are found in an early-stage human embryo," per Live Science. Globus says few doctors in his field have seen such cases. The girl is expected to make a full recovery and is already at home with her mother and three siblings. (A woman found out there was a fetus in her stomach at age 17.)