Gabrysia was operated on at just seven weeks of age by a team of specialists from the Silesian Center for Heart Diseases in Zabrze, southern Poland.

When she was born, she had only one atrium, one ventricle and two valves in her heart. A healthy human heart normally has two atriums, two ventricles and four valves.

The transplant operation was challenging because of the small size of the patient, but it turned out to be successful.

Now, at three months old, Gabrysia feels “fine,” her parents have said. The family went for a check-up on Thursday.

Gabrysia’s mother told Polish radio broadcaster RMF FM that her happiness is “overwhelming.”

“It is impossible to describe. We owe everything to the doctors,” she said.

Gabrysia will have to take immunosuppressive drugs throughout her life and will be regularly checked by doctors.