بسم الله الرحمن الرحيم
Shaykh Uthaymeen -Rahimahullah- was asked concerning a woman who woke up for fajr after the sun had risen and realised she was now menstruating.
“She has to make up the fajr prayer after her menses, because the origin is that she was pure; i.e. she knows she was not menstruating when she went to sleep, she woke after the time of fajr, so all she knows for certain is that she was menstruating after the time of fajr came in and therefore she makes up the fajr prayer.”
The Shaykh went on to say:
“It saddens me that she did not wake for the fajr prayer except after the sun rose, because it is an obligation upon mankind that they guard themselves and that they take the required means so that they can wake and pray on time.”
Majmoo’ Fataawa 219/12