Do Both Parents Have to Be Cystic Fibrosis Carriers for a Child to Get It?

My son has alot of Respitory issues and has alot of weight gain problems as well. He is going tommorrow tohave a sweat test done…I have talked to my midwife to confirm that my CF carrier screening that was done during my prenatal blood work was negative but she was unsure about both parents having to be carriers for my child to get it. I have serached all day for answers and can not find a definite answer. PLEASE HELP!