Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.9861
Fataawa Ramadhaan – Volume 2, Page 588, Fatwa No.573
Question: What is the ruling regarding a woman who gave birth during Ramadhaan a number of times [over a period of a few years] and was unable to make up the days [of fasting] she missed?
Response: It is obligatory upon the woman who gave birth in the month of Ramadhaan to make up the days she was unable to fast in Ramadhaan afterwards. And if she delayed making up the fasts until the [arrival of the] next Ramadhaan without [an Islaamically acceptable] reason, then it is obligatory upon her to feed a poor person for everyday she missed in addition to making up the fasts [she missed]. However, if the delay in making up the fasts was for an Islaamically acceptable reason, then it is obligatory upon her to just make up the number of days she missed.
And with Allaah lies all success, and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.