What is the expiation for not fasting missed days from Ramadan due to illness or pregnancy? Can money be paid as expiation for them? And what is incumbent upon one who vowed to name his son Yusuf, then wished to retract his vow?

If the excuse of pregnancy is continuous from before Ramadan (definition), there is no expiation (kaffarah (definition)), but only making up the missed fasts (qada'). Making up Ramadan fasts is not obligatory immediately, unless there remains only a period equal to the number of days to be made up before the next Ramadan. The questioner must make up the Ramadan fasts she missed due to treatment. If the delay in making them up was without a valid excuse until the next Ramadan arrived, then in addition to making up the fasts, an expiation for the delay is required, which is feeding one poor person for each day, amounting to 750 grams of the staple food of the country. This expiation is not repeated. However, if she was unable to make up the fasts due to a continuous excuse, then there is no expiation in that case.

As for the vow mentioned, it is a vow concerning a permissible act, which most jurists consider not to be binding. Thus, fulfilling it is not obligatory, and there is no harm in retracting it. The Hanbalis, however, view it as binding, and the person who made it has the choice between fulfilling it or offering an expiation for breaking an oath (kaffarat yamin (definition)).