As far as Islamic Shair`ah is concerned, once you have got your menses, your fast is broken and you are allowed to eat and drink like everyone else who is excused from fasting due to illness, traveling, pregnancy, or breastfeeding.
Dr. Rif`at Fawzi, former professor of Shari`ah at Cairo Univ. , states: “As a woman, If you got your menses before sunset (the time for iftar), then your fast is broken and you have to make up for this day after Ramadan. However, it should be clear that even if this day is not counted, you will be rewarded for abstaining from food and drink all this day. May Allah reward you and accept your fasting.”