Must I fast Ramadan, given that I am pregnant and doctors have warned me against fasting due to gestational diabetes, and that my previous pregnancy ended in fetal death, possibly due to gestational diabetes and fasting? And must I offer expiation for each day I do not fast, or at the end of the month?

If doctors advise not to fast due to gestational diabetes, then fasting Ramadan (definition) is not obligatory, and there is no expiation if the fasting is broken out of fear for oneself. Rather, it is obligatory to make up the fasts once the impediment is gone. If the fasting is broken out of fear for the fetus only, then both expiation (Fidya) and making up the fasts are obligatory, which is feeding one poor person for each day.