I ditto Wander's post, but I also think that it's important to talk out a decision like this. Do you have CF? Does your partner? Was your baby diagnosed with CF??? I don't think anyone has a right to judge you based on your situation, but giving us some info. about yourself can help us help and understand you.
I do know that the few people who I know personally who have aborted (for various reasons, NONE of them being a medical problem with the child, but rather for their own convenience) deeply deeply regret it. Just my experiences though.