Baby Born With Half-Formed Twin Sister Growing Inside Her

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A baby girl was born with her twin sister inside her, half-formed, but still growing via its own umbilical cord.

The incredibly rare phenomenon was first documented in 1808, with fewer than 200 cases reported since, but the case in Columbia was the first time that the condition has been picked up before birth.

Itzamara was born on Feb. 22 in Barranquilla, Colombia, via Caesarian section and whisked straight to the operating table, reported local media.

Doctors knew that what they had first thought was a liver cyst was, in fact, a twin fetus, which had not fully formed, that was still growing, risking the life of the newborn.

Using keyhole surgery, they removed a two inch, half ounce fetus, which had arms and legs but no heart and no brain.

The condition, known as “fetus in fetu” occurs is formed in a similar way to Siamese twins.

When an embryo divides a week after conception, identical twins are produced. But when division happens in the second week, the twin embryos fail to fully separate, resulting in Siamese twins. If it splits in the third week, the twin embryos do not form equally: only one develops a connection to the mother that grows into an umbilical cord. The other embryo draws its nutrients from the stronger twin embryo, which grows around it.

Such cases are incredibly rare and have always been discovered after birth when doctors operate on what they believed to be cysts.

In the case of Itzamara, as 25-week scan had revealed what medics thought to be cysts. But a further scan at 35 weeks revealed something new, obstetrician Dr. Parra-Saavedra told Channel1. 

“Analyzing it with 3D ultrasound, 4D, and with color Doppler ultrasound we saw that what I really had was not a cyst but an amniotic sac inside which there was an embryo, it measured 45 millimeters and this surprised us a lot inside a fetus,” he said.

Two weeks later, another scan revealed that the fetus had grown over 20-30 percent in mass, potentially endangering the life of the unborn baby, risking crushing its internal organs.

The as-yet-unborn baby’s mother, Monica Vega had also begun to develop preeclampsia.

The doctors decided the best course of action was for the baby to be born by emergency caesarian, and the fetus removed as soon as possible.

“Once we cut the umbilical cord [of the attached twin], the baby’s life ended because it was surviving off its sister,” Parra-Saavedra told the Herald.

According to Parra-Saavedra, the family found it hard to grasp what was happening at first.

“After we showed them photos, videos, and scientific evidence they understood the phenomenon and allowed us to go ahead with the necessary steps [to handle it],” he told the Herald. 

“It’s difficult explaining to someone that they’re experiencing what happens in one in a million because obviously they have never heard of it, ever seen it, and in fact, most people don’t know this happens,” he said.

He said described the phenomenon as “one of the strangest and most fascinating things you can see in maternal-fetal medicine.”

In 2017, a baby was born in Mumbai with his own half-formed twin brother inside his stomach.

The deceased twin—which was nearly 3 inches in length and had formed in the other baby’s abdomen—had a brain, arms, and legs, according to the India Times.

Dr. Neena Nichlani, who delivered the twins, said the mother and child are quite lucky.

“It can be implanted in skull, abdomen, or tail bone of the host,” Dr. Nichlani said.