Quran At-Talaq 65:4
وَٱلَّٰٓـِٔي يَئِسۡنَ مِنَ ٱلۡمَحِيضِ مِن نِّسَآئِكُمۡ إِنِ ٱرۡتَبۡتُمۡ فَعِدَّتُهُنَّ ثَلَٰثَةُ أَشۡهُرٖ وَٱلَّٰٓـِٔي لَمۡ يَحِضۡنَۚ وَأُوْلَٰتُ ٱلۡأَحۡمَالِ أَجَلُهُنَّ أَن يَضَعۡنَ حَمۡلَهُنَّۚ وَمَن يَتَّقِ ٱللَّهَ يَجۡعَل لَّهُۥ مِنۡ أَمۡرِهِۦ يُسۡرٗا ٤
Translation
And those who no longer expect menstruation among your women - if you doubt, then their period is three months, and [also for] those who have not menstruated. And for those who are pregnant, their term is until they give birth. And whoever fears Allāh - He will make for him of his matter ease.