An infant who died on a United Airlines flight diverted to Milwaukee Wednesday had been born with a heart defect and was headed home to South Dakota after treatment at a Michigan hospital.The 2-month-old baby and family were from South Dakota, but he was born with a heart defect, Pulmonary Atresia, according to an investigation report from the Milwaukee County Medical Examiner's office. He lived almost all of his life in medical unit at the University of Michigan children's hospital in Ann Arbor.The infant was released from the Michigan hospital Wednesday and given oxygen for a flight back from Detroit to Denver. But the infant became fussy and then started to breathe rapidly and heavily Wednesday afternoon when the flight was about 20 minutes out of Milwaukee, according to the report.