Jilian I totally believe your theory! My dd was also born with a chd (not nearly as serious--she had a medium VSD), at home. We didn't get an ultrasound even though I had originally planned to. At the last minute I just felt wrong about it and called and cancelled the appt. Later on, about 34 weeks, the mw heard a couple irregular hbs with the doppler, but I told her I wanted to think about it before deciding if we should do more screening. I called my mom and she said I'd had something similar so I opted to not do more screening. I was upset though...I felt something was "off" and I really wanted to know what. I kind of prayed and meditated about it and I asked the baby "what will I do if you're not ok? What if you don't make it?" And this little voice inside me says "You'll be ok, mama. I have a problem with my heart, but I am fine." I was shocked and didn't tell anyone, fearing most of all that it might be true, but also that I might be losing my mind to paranoia...
Well she was born at home, had apgars of 7 and 9. Everyone was concerned about her color (very dark, not blue but like a deep tan--I thought it was from my NA heritage) and her fast breathing, but she usually was just under the cut off for tachypnea so we stayed home. I was so worried about her breathing and brief apnea spells I sat up with her the entire first night and second night. On day 3 she started having retractions, the murmur was more pronounced, and the blue spells were more noticable (for one thing, I didn't know from newborns...I thought they all were funky shades of purple brown.) So we took her to the ER.
In the ER tons of doctors were swarming around and before the cardiologist got there, one dude wanted to prep her for surgery. They threw out about 39 different diagnoses before he got in there with the echo and made the definitive one. Even in the brief time she was in the NICU her condition improved and the hole in her heart actually got smaller. I have no way of KNOWING this is true but I feel instinctually pretty certain that if I had had a hospital birth I would have been induced before 40 weeks, she would have been a lot smaller and weaker, the hole in her heart would have been a lot more serious, and she would have had a much harder time stabilizing. And, I strongly suspect there was a good chance she would have been subjected to life-threatening surgery prematurely.
As it was she was able to heal without surgery, and so quickly the cardiologist about fell over when we went in for the follow up.
I really think homebirth can be a lifesaver. I totally believe it.

to you and little Evan.