Reference: Fataawa Ramadhaan – Volume 1, Page 375, Fatwa No.334
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-`Ilmiyyah wal-Iftaa. – Fatwa No.6608
Question: My wife, who is currently breast feeding, has three or four Ramadhaan’s worth of fasts to make up as she was unable to fast them because she was either pregnant or breastfeeding [at the time]. So she asks is she allowed to feed a person for each of the days she has to make up instead of fasting them because she finds it extremely difficult (daunting) to make up the fasts for three or four Ramadhaan’s worth?
Response: There is no harm in her delaying making up the fasts if the reason is due to her experiencing hardship due to pregnancy or breastfeeding; And whenever she is able [to make up the fasts] she must hasten to make them up because she is currently legally classified as one who is ill, as Allaah (Subhaanahu wa Ta’aala) says:
…and [with that] she is not required to offer any expiation.
And with Allaah lies all the success, and may Allaah send prayers and salutations upon our Prophet Muhammad ﷺ and his family and his companions.