All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
A woman is permitted to take pills that delay menstruation if there is a lawful need for that. For example, fearing to be left behind by her Hajj orOmrahcampaignbecause she isn`t ritually pure to finish rituals on time. Also, keenness on fasting the whole month of Ramadan because she isn`t sure that she can make up for the missed fasts. But, this is provided that the side effect of the medication isn`t well-established and the husband`s permission is secured.
In fact, scholars have clarified the ruling of Sharia on this matter:
Al-Bahwati, a Hanbali jurist, said, "A woman is permitted to take a lawful medication to stop her menses as long as she made sure that it is harmless. Al-Khadi said, "Taking such medication isn`t permitted save with husband`s approval………A woman is permitted to take a lawful medication to induce her menses, provided that she doesn`t do so in order to avoid fasting Ramadan"{Kash-shaaf Al-Khinaa`, 1/218}.
Ibn Rushd(May Allah bless him) said, " When Imam Malik was once asked about the woman who is about to have her menses and was prescribed a certain medication to delay it? He replied, "That is disliked." Ibn Rushd said that Malik disliked that to prevent harm."{Mawahiib Al-Jaleel, 1/538}.
However, it is worth reminding that a woman who is having menses is rewarded for not fasting Ramadan, because by that she is adhering to the command of Allah, The Almighty. Therefore, a Muslim woman is advised to spare her body the side effects of such medication, because menstruation is Allah`s decree for women. And Allah knows best.