What should I do about making up for missed Ramadan fasts, knowing that I broke my fast out of fear for the fetus, and I haven't made them up yet due to breastfeeding? Can I just pay expiation?

If breaking the fast in Ramadan is due to fear for the fetus, then the woman must make up the missed days (qada') and feed a poor person for each day (approximately 750 grams of rice), which is the most authoritative ruling. If the next Ramadan begins before she has made up the missed fasts due to a valid excuse, there is no expiation for delay, and she should make up the fasts after the excuse is no longer present. If the fear for the infant or herself continues into the next Ramadan, it is permissible to break the fast. If the fear is for herself, or for herself and the infant, then she only needs to make up the fasts. If the fear is for the infant alone, then she must make up the fasts and feed a poor person.