Sally is 22 years old and in good health. She presents to the GP surgery with her partner John. Sally’s mother had Cystic Fibrosis and unfortunately recently passed away. John is a known carrier of Cystic Fibrosis. They are thinking of starting a family in the near future and wants your advice about the risk of having a child with Cystic Fibrosis.
Which one of the following statements is least correct?