Twenty-weeks pregnant with her second child, Laura Diltz and her husband, Andy, knew something was not quite right when the ultrasound technician took longer than usual and asked them to stick around and speak with a doctor.

That day, the Diltzs learned from Johns Hopkins pediatric cardiologist Candace Gibbin  that their unborn baby had transposition of the great arteries, a heart defect in which the main arteries (the pulmonary artery and the aorta) that carry blood to and from the heart are transposed (switched.)  And they learned that they were having a boy.

HEAR Calvin's parents tell their story at Radiothon 2010 

The emotional impact was compounded for Andy. His own mother had lost two babies to structural heart defects before he was born.

In the months leading up to Calvin’s birth, Laura and Andy had a crash course in pediatric cardiology. They read voraciously and learned more than they ever thought they ever would about the human heart. At Hopkins Children’s, pediatric heart surgeons Duke Cameron  and Luca Vricella  met with them and went over all the details.

“It was very difficult but it was also wonderful that they were so honest and upfront,” says Andy.

Calvin was born on a Monday afternoon and taken to the neonatal intensive care unit that day. Seventy-two hours later, he underwent open-heart surgery. Throughout the seven-hour surgery, Laura and Andy received hourly updates from the surgical nurses.

Calvin’s surgery was a complete success and he had a smooth post-op recovery. To protect against infection and injury as he grew, Calvin had to spend the first years of his life at home, and out of daycare. For Andy, who could have never imagined being the stay-at-home parent, the time spent with his two children, he says, was priceless. And the family learned that it could live nicely on one income.

Calvin continues to see pediatric cardiologists at Hopkins Children’s for routine checkups, and so far he’s gotten a clean bill of health. Now in preschool, he loves to dance and play with trains. When the day comes that he wants to play sports, he’ll first need a stress test. Until then, it’s full steam ahead for Calvin and his sister Ava, 6.