It seems very difficult to establish the likelihood of fertility after an ovarian tube ligature. I recommend you consult a gynecologist for that specific concern. Regarding your concerns about heart health for a future child...If the reason for the first child's heart condition was genetic, then the second child may also have the same problem. But if the reason for heart problem was another factor (viral infection, medicament, radiation etc.) that acted on the fetus during the embryonic development, then the second child will probably not have the same heart condition. You can contact Medicare directly to confirm your benefits and allowances for pregnancy. Most health insurance plans require extensions in cases of pregnancy and birth.