Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.10138
Fataawa Ramadhaan – Volume 2, Page 590, Fatwa No.575
Question: My wife gave birth to a baby just before the blessed month of Ramadhaan, by about seven days, and she became pure [completed her postpartum bleeding] before the arrival of the month of Ramadhaan. [Subsequently,] is her fast complete or is she required to make up the days, knowing that she only fasted whilst she was pure [from the postpartum bleeding]? Advise us and may Allaah reward you all with good.
Response: If the situation is as described, then the fast of your wife during the month of Ramadhaan whilst she was pure (in the state of purity – free from postpartum bleeding), is correct and she is not required to make up the days.
And with Allaah lies all success, and may Allaah send prayers and salutations upon our Prophet Muhammad ﷺ and his family and his companions.