Narrowly avoiding death, Gonzalo Pardo Sanchez, of Spain, became the first unborn baby to thrive after an operation to clear his windpipe. Now he’s a healthy 10-month-old with no idea of the odds he overcame.

Doctors discovered a membrane that blocked the unborn baby’s larynx and prevented his lungs from evacuating fluid through the trachea. The buildup of liquid put intense pressure on his heart.

This rare condition is called CHAOS — congenital high airway obstruction syndrome. Boston Children’s Hospital reports “more than a dozen cases” of CHAOS since 1989, though the hospital believes the condition is under-counted because so few affected fetuses make it to term.

Prior to Gonzalo’s diagnosis, in-utero surgery to correct CHAOS had been attempted seven times around the world. The unborn children either died or suffered severe complications, according to The Times of London.

At 21 weeks into Maria Jose Sanchez’s pregnancy, however, specialists in Barcelona were able to turn her baby to access the growth, avoiding a slip by even a millimeter that could have proved fatal to the child. Then they punctured the membrane with endoscopes to clear the airway.

The fetus weighed just short of a pound at the time, Spanish newspaper El Pais wrote. He was delivered weeks later without respiratory distress.

“We came to Barcelona to abort, without hope of saving our son,” the father, Francisco Pardo, told Spanish outlet 20Minutos. Pardo added that he and his wife felt they had nothing to lose by trying the procedure.

The news site added that Gonzalo shows no after-effects and has passed all his medical exams.

In April, ABC News reported another breakthrough in treating a cardiopulmonary birth defect. A toddler born without a trachea was implanted with one fashioned from nanofiber mesh covered with cells from her bone marrow.