Qur'an 65:4

وَٱلَّـٰٓـِٔى يَئِسْنَ مِنَ ٱلْمَحِيضِ مِن نِّسَآئِكُمْ إِنِ ٱرْتَبْتُمْ فَعِدَّتُهُنَّ ثَلَـٰثَةُ أَشْهُرٍ وَٱلَّـٰٓـِٔى لَمْ يَحِضْنَ ۚ وَأُو۟لَـٰتُ ٱلْأَحْمَالِ أَجَلُهُنَّ أَن يَضَعْنَ حَمْلَهُنَّ ۚ وَمَن يَتَّقِ ٱللَّهَ يَجْعَل لَّهُۥ مِنْ أَمْرِهِۦ يُسْرًا

“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.”

At-Talaaq 65:4 · Saheeh International