Answer:
With respect to the missed fasts: if he abandoned them because of illness and never regained the strength to make them up until he died, nothing is required of him, for he is excused.

However, if he recovered after his illness, was physically able to make up the days, yet procrastinated until he passed away, then feeding the poor becomes obligatory on his behalf: for every missed day one needy person must be given half a sâʿ (about 1.5 kg/3.3 lb) of the staple food eaten in that country.

As for the monetary debt he left behind, that remains the right of his creditor. If he has an estate, the debt must be settled from it before anything else. If he left no estate, his next of kin or guardian should pay it off to clear him of liability and free him from the bond of debt. Indeed, any Muslim who learns of his situation—even if not a relative—is encouraged to discharge this debt as an act of kindness and to relieve a fellow Muslim of his obligation.

—
Making Up Fasts Missed During Pregnancy
Question: Two years ago, during the month of Ramadan, I was ill and could not fast for seven days. Afterward I fed one needy person for each missed day. Is that sufficient, or do I still have to make up those days? Please advise, and may you be rewarded.

Answer: You must both feed the poor and make up the fasts. If you broke the fast because you were pregnant, two things are due: feeding and making up the days. The feeding has already been done; what remains is to make up the fasts. If, however, you missed the fasts solely because of your own illness, then only the make-up fasts are required, without any feeding.