The mass blocked passage of blood from the abdomen to the heart, with the fetus tetering on the verge of heart failure.

Doctors said it would have been impossible for the child to breathe with the mass in the chest. Without surgery, the child would have died of heart failure or lack of oxygen shortly after birth.

The baby, an eight-pound boy from Round Rock, Texas, was at 37 weeks gestation and delivered by a two-hour modified Caesarean section.

During the operation, surgeons cleared the child's airway, attached breathing tubes and intravenous lines, and opened the right chest to deliver the mass.

Immediately following the delivery, they completed removal of the mass in a delicate two-and-a-half-hour procedure.

The infant almost did not make it to birth and, in fact, was deteriorating rapidly in the hours before the procedure, Olutoye stated.

"The mass was pressing heavily on the chest and lungs, making it impossible to expand the child's lungs”, he explained.

Besides, the mother was beginning to suffer a condition known as "mirror syndrome", in which her health deteriorates along with that of the infant.

Said Olutoye: "The baby suffered from an extremely large and rare mass, and we are thrilled to have such an excellent outcome".

While other EXIT procedures have been done for cystic lung lesions, this is the first reported EXIT to resection for a fetus.

Olutoye worked with Dr. Mary Day and other members of the Division of Maternal-Fetal Medicine in the department of obstetrics and gynecology at BCM. He has performed eight EXIT procedures to date.

During EXIT, surgeons partially remove the fetus from the womb and perform surgery while the fetus remains attached to the umbilical cord. When the procedure is complete, the baby's umbilical cord is cut and he or she is delivered.