Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
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.
There is nothing in the authentic Islamic sources that makes it obligatory on you to maintain your fast and abstain from food and drink once your menses has begun.
In his response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
There is nothing in the sources that makes it obligatory on you to maintain your fast and abstain from food and drink once your menses has begun; for once menses has started, your fast is void and you are allowed to eat and drink like everyone else who is excused from fasting due to illness, traveling, pregnancy, or breastfeeding. It is important to stress, however, that you ought to make up for the fasts you have thus missed.
There is no proof for those who claim that women, who have started menstruating during midday or after, must stay away from food and drink. It is simply a popular misconception or faulty interpretation among some people; it has no sound basis whatsoever in the authentic sources of the Shari`ah.
In other words, there is nothing in the sources of Shari`ah that requires a person who has broken his fast due reasons that are prescribed in the Shari`ah to stay away from food and drink. To insist upon this condition is nothing short of unwarranted rigidity. Islam in its pristine form is free of such extremism and rigidity. The Prophet (peace and blessings be upon him) said, “This religion of ours is simple and easy to follow; whoever makes it hard upon will only be defeating himself/herself.” (Al-Bukhari)
Allah Almighty knows best.
Excerpted, with slight modifications, from: www.islam.ca