What's the risk that your child will get cystic fibrosis?
If you and your spouse both carry the faulty allele for cystic fibrosis, you might be wondering what the chances are that your child will get the disease. In this situation, it's all about probability. Because carriers have a faulty and a good gene, there is a 50% chance that each parent will pass on the bad allele. The chance of both parents giving their child the bad gene is about 25%, and the chance of their child becoming a carrier themselves is 50%. Essentially, if a couple is a carrier positive for both parents, the child has a 1 in 4 chance of getting cystic fibrosis.