What is the ruling on making up for the days not fasted in the past Ramadan due to pregnancy, childbirth, and continuous breastfeeding of a sick infant, and when must they be made up, and is expiation alone sufficient?

Days of Pregnancy: If you break your fast out of fear for yourself or for the fetus, then you only have to make up for those days (qada'). If you break your fast out of fear for your fetus only, then in addition to making up for those days, you must feed one poor person for each day.

Days of Breastfeeding: You are permitted to break your fast, and you must make up for those days (qada'). In addition to making up for those days, you must feed one poor person for each day you break your fast. This is the more cautious approach.

Days of Postpartum Bleeding (Nifas): You are only obligated to make up for those days when you are able. If you are unable to make them up until another Ramadan or Ramadans arrive, then there is no blame upon you, and you make them up when you are able, "because Allah, Exalted be He, does not burden a soul beyond its capacity."