TODAY | January 27, 2013
>>> called a miracle baby , a three-month-old born with her heart outside her chest. as katy tur reports, she is proving that survivors come in all sizes.
>> hey, look at mommy.
>> to say audrina cardenas is lucky would be to discount her tremendous strength. the three and a half-month-old is fitted with a shield and about to go home for the first time.
>> it is a very, very big step. it has been a blessing to be able to say we are finally going home .
>> reporter: the baby girl was born with one-third of her heart outside of her body, a rare congenital defect . only 8 babies out of every 1 million are born with the defect. 90% are stillborn or die within days. she was diagnosed at 16 weeks in the womb. you can see her holding her own heart in this mri. she was born full-term on october 16th and immediately rushed into surgery.
>> as a mother, you look at her just like you look at in he other child. that's your baby. in a mother's eyes, sometimes you don't see her any other way. she smiled after the successful surgery. now, you can see her tiny heartbeating just below her skin.
>> she doesn't have a sternum. she doesn't have anything over her heart besides the skin and the little muscle.
>> reporter: without a sternum, the pink shield is deseenigned to protect her chest and her tiny heart as it gets stronger.
>> doctors may end up taking a piece of the child's rib and putting it in the location of the breast bone so that it, in turn, will turn into the new breast bone .
>> reporter: doctors have been watching over her since the day she was born. on friday, they had a rare chance to give this mother and daughter a happy good-bye.
>> thank you. take care.
>> good-bye. we'll see you soon.
>> we wish her all the best. amazing how far medical science has come.
>> it really is.