I can speak to the g-tube a bit. First off, the CF center I attend has had several women with g-tubes who have been pregnant, so yes, it does happen. I'm not pregnant, but we are in the process of trying to conceive. I ended up getting the g-tube because we wanted to conceive. I have been doing well all my life FEV wise, but after a major infection several years ago, I never really got back to baseline. I kept getting sick, losing weight, getting sick and the cycle continued. After ruling out all the other possibilities, we basically decided that my quickly declining weight was the the problem and pregnancy was not going to happen unless I got my weight up. I had tried all other methods, until I finally decided to get the tube. Pre g-tube, my FEV was 80%, a year after, my FEV is 97%, with little to no need for antibiotics. I still use my tube and will most likely need to, especially when pregnant. The idea is that by being aggressive with the tube, we were able to prevent major lung damage and recover the lung function that was lost.
I say all this because I think there is a negative connotation about g-tubes; that it means someone tends to be sicker from the CF perspective, and maybe not in the best health to be pregnant. When it was first suggested to me, I sure thought it meant I was getting sicker. But for me, it was what I needed TO get healthy. I personally think we will start to see more g-tubes in the CF population, as centers are suggesting them sooner as the correlation between BMI and FEV is quite clear.
According to my CF center, OB, and the surgeon who placed the tube, there are NOTHING says that because you have a g-tube, you can't be pregnant. As it was explained to me, as the baby grows, the internal organs shift and the tube is flexible and will shift with it. They did say I might need a longer button to allow for that shifting. Obviously, I assume towards the end it will be uncomfortable, but certainly not impossible.
Keep in mind, there are many reasons that g-tubes are utilized for a variety of GI disorders. Back when considering having it placed, I did a google search in which women with g-tubes were able to have children without problems with the tube. Of course its not common, but from what I could find, definitely not contraindicated.
I would talk with your doctor, but mine assured me that the g-tube itself was fine to have and even use during pregnancy.