Blood in lungs

So I'm 19 weeks one day today I had my fetal survey this morning and I was told they found some blood in the babys lungs they informed me that this could be caused by a chromosomal disorder cystic fibrosis or the fact that I had some bleeding in my early pregnancy due to subchorionic hemorrhage they pretty much ruled out the chromosomal disorder based on my initial test for it I carry the gene for cystic fibrosis my boyfriend is going to be tested for it if he comes back negative then that only leaves the hemorrhage as the cause of the bleeding if he comes back positive then cystic fibrosis is a strong cause of it has anyone ever had this occurrence before?  Not specifically a positive test for cysticfibrosis  but more so the presence of blood in the babys lungs