She took birth control pills and her periods stopped; should she pray and fast?
Question

                The use of birth control pills can cause a women to stop having her monthly periods/menstruation all together till she stops using the pills. In such circumstances what is the ruling for her on praying and fasting? Does she continue praying without any breaks? The sister is taking the pills for a legitimate reason and not because she doesnt like menstruation.
Praise be to Allah.
    
    Firstly: 

    
    There is nothing wrong with using contraceptives when there 
    is a need to do so, if that is with the permission of the husband and under 
    medical supervision. For more information, please see the answer to 
    questions no. 32479 and 21169. 

    
    Secondly: 

    
    If the monthly periods have stopped because of taking those 
    pills or for some other reason, the woman is deemed to be in a state of 
    purity, so she can do everything that women who are in a state of purity do, 
    such as fasting, praying, and sitting in the mosque, because all of these 
    things are only disallowed because of the menstrual blood. If she is not 
    bleeding, then the prohibition does not apply and she may do whatever women 
    who are in a state of purity do. This is indicated by the words of the 
    Prophet (blessings and peace of Allah be upon him) to the woman who was 
    suffering from istihaadah (irregular, non-menstrual bleeding): “If it is 
    menstrual blood, it is dark and recognisable; when it is like that, then 
    refrain from praying, and when it is the other type, then do wudoo’ and 
    pray.” Narrated by Abu Dawood (304); classed as saheeh by Shaykh al-Albaani 

    
    It says in al-Mawsoo‘ah al-Fiqhiyyah (18/327): The 
    Hanbalis clearly stated that it is permissible for a woman to take 
    permissible kinds of medicine in order to stop menses, if it is free of 
    harmful effects; that is subject to the husband's permission, because he has 
    a right to have a child. Maalik regarded it as makrooh, lest the woman cause 
    harm to her body by doing that. … If the woman takes medicine and her 
    periods stop, then she is deemed to be in a state of purity. End quote. 

    
    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: If 
    she takes something to prevent menses, and she does not have a period, then 
    she should carry on praying and fasting, and not break the fast and make it 
    up later, because she is not menstruating. The ruling is connected to the 
    reason. Allah, may He be glorified and exalted, says (interpretation of the 
    meaning):

    
    “They ask you concerning menstruation. Say: that is an Adha 
    (a harmful thing for a husband to have a sexual intercourse with his wife 
    while she is having her menses), therefore keep away from women during 
    menses and go not unto them till they have purified (from menses and have 
    taken a bath). And when they have purified themselves, then go in unto them 
    as Allah has ordained for you (go in unto them in any manner as long as it 
    is in their vagina). Truly, Allah loves those who turn unto Him in 
    repentance and loves those who purify themselves (by taking a bath and 
    cleaning and washing thoroughly their private parts, bodies, for their 
    prayers, etc.)”

    
    [al-Baqarah 2:222]. 

    
    When this harmful thing is present, the rulings on it are 
    applicable; when it is not present, the rulings are not applicable.

    
    End quote from Majmoo‘ al-Fataawa, 19/260 

    
    And Allah knows best.