Yes it is possible...I am not steve but i am getting a pHd in molecular bio if that makes any difference to you. New mutations can arise at any time in the germ cells (the cells that make egg and sperm). Sequencing by ambry will detect them. The other possibility is that you or your husband has two CFTR mutations. It could be that this other mutation does not cause much disease in your husband or you but due to your son's genetics affects him much more severly. I'm really sorry to hear you are going through this!