Is it sinful for a terminally-ill woman to have relations with her husband, knowing that if she becomes pregnant there is a high chance she will die before the baby can be born?

Or a variant scenario: What about a woman who is condemned by law to be executed on a less-than-nine-months-hence date? (I'm not sure a government so cruel as to execute a pregnant woman would be so generous as to allow conjugal visitation of prisoners, but stranger things have happened I'm sure.)

So in both cases, there is still at least the possibility of a positive resolution. Perhaps the woman will miraculously regain her health. Perhaps the government will have a change of heart and pardon her, or at least postpone her sentence. But if either would seem extraordinarily unlikely, how ought we to think?