A team of American doctors has performed groundbreaking brain surgery on a baby who is still in the womb to treat a rare blood vessel abnormality inside the brain, according to CNN.

This rare brain condition is known as "Venus of Galen malformation," and the operation was conducted at Brigham and Women's Hospital and Boston Children's Hospital.

The condition occurs when the blood vessel that carries blood from the brain to the heart doesn't develop correctly. The malformation results in an overwhelming amount of blood stressing the veins and heart and can lead to a cascade of health problems, reported the news outlet.

"Tremendous brain injuries and immediate heart failure after birth are the two big challenges," Dr. Darren Orbach, a radiologist at Boston Children's Hospital and expert in treating VOGM, told CNN.

Giving the details of the complication, he said that typically, infants are treated after they're born using a catheter to insert tiny coils to slow down blood flow. However, the treatment often happens too late.

"Despite advancements in care, "50 to 60 percent of all babies with this condition will get very sick immediately. And for those, it looks like there's about a 40 percent mortality rate. About half of infants that survive experience severe neurological and cognitive issues," Orbach said.

According to CBS News, Baby Denver was growing normally inside her mom when, on a routine ultrasound, doctors discovered she had this rare blood vessel abnormality inside the brain. Many babies with this condition develop heart failure or brain damage and often don't survive. In fact, Denver's heart was struggling, and the malformation was getting dangerously large.

So, at 34 weeks of pregnancy, a team at Boston Children's and the Brigham were able to repair her malformation while she was still in the uterus, using ultrasound guidance, a needle similar to those used for amniocentesis, and tiny coils that were placed directly into the abnormal blood vessels to stop blood flow.

What is a vein of Galen malformation?

According to Boston Children's Hospital, a vein of Galen malformation (VOGM) is a type of rare blood vessel abnormality inside the brain. In VOGM, misshapen arteries in the brain connect directly with veins instead of connecting with capillaries, which helps slow blood flow. This causes a rush of high-pressure blood into the veins. This extra pressure in the veins can cause a number of problems.