Lynn Cassidy claims it was a miracle that her baby Ave was almost fully cured from her illness after a blessing from the Holy Father.
The family had travelled to Rome in April 2014 to watch the canonisation of John Paul II and John XXIII.
Speaking to American media company KPNX Lynn said: "It was raining, we were told that if we stood on a barricade in St. Peter's Square, the metal fences in front, the Pope would come by in his 'Pope'-mobile."
She said her husband Scott held Ave in the air as the Pope drove past: "It was like the Lion King.
"The secret service person, Johnny, stopped and took her from Scott and held her up to the Pope.
"The Pope asked my husband, 'How old is she? What's her name?' He told (the Pope) she has two holes in her heart.
"When we got home in May, we went back to the cardiologist for a check-up. One of the holes was completely closed and one was half the size."
Ave was born with Down syndrome, eye problems and hearing complications related to the two holes in her heart.
"I mean it's possible that it closes just over time," she said. "But when you see the picture that the professional photographer took, his hand is here and he's a servant of God."
"It seems like it was really meant to happen," she added, "and it's as close to a miracle as we'll ever see, I'm sure."
Ave is said to be 'happy and healthy' after two eye surgeries and her heart is now working properly.
