The scholars agree
that it is obligatory for menstruating women and women with
post-natal bleeding to break the fast and to make up for the missed
days later on. Al-Bukhari and Muslim quote 'Aishah as saying:
"Whenever we were in menstruation period during the lifetime of
the Prophet, peace and blessings be upon him, he used to order us to
make up for the days of fasting that we missed but he’d not order
us to make up for the prayers we missed..