From the knowledge I have of CD and heart disease I would tend to think your physician is right. The strain on your body with the pregnancy may have thrown you into CHF. You were already ill with the CD and your heart had to do all the work for pumping blood for you and you baby. This is my own opinion and I think you have the right to get second opinion if you feel you need one.
I am sorry you just got back your appetite and they put you on low sodium diet but I feel you are a strong person and you will do what you must to keep the CHF at bay.
"If you doubt you can accomplish something, then you can’t accomplish it. You have to have confidence in your ability, and then be tough enough to follow through.”