Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.120.
Section : Those who must make up the missed days.
The scholars agree that it is obligatory for menstruating women and women with post-childbirth bleeding to break the fast and to make up the missed days later on. Al-Bukhari and Muslim recorded that ‘Aishah said: “When we would have our menses during the lifetime of the Prophet, we were ordered to make up the days of fasting that we had missed but were not ordered to make up the prayers that we had missed.