Once one of the wives of the Prophet ﷺ did Iʿtikaf along with him and she was getting bleeding in between her periods. She used to see the blood (from her private parts) and she would perhaps put a dish under her for the blood. (The sub-narrator ʿIkrima added, ʿAisha once saw the liquid of safflower and said, "It looks like what so and so used to have.")  

أَنَّ النَّبِيَّ ﷺ اعْتَكَفَ مَعَهُ بَعْضُ نِسَائِهِ وَهْىَ مُسْتَحَاضَةٌ تَرَى الدَّمَ فَرُبَّمَا وَضَعَتِ الطَّسْتَ تَحْتَهَا مِنَ الدَّمِ وَزَعَمَ أَنَّ عَائِشَةَ رَأَتْ مَاءَ الْعُصْفُرِ فَقَالَتْ كَأَنَّ هَذَا شَىْءٌ كَانَتْ فُلاَنَةُ تَجِدُهُ  

"One of the wives of Messenger of Allah ﷺ joined him in Iʿtikaf and she noticed blood and yellowish discharge (from her private parts) and put a dish under her when she prayed."  

قَالَتِ اعْتَكَفَتْ مَعَ رَسُولِ اللَّهِ ﷺ امْرَأَةٌ مِنْ أَزْوَاجِهِ فَكَانَتْ تَرَى الدَّمَ وَالصُّفْرَةَ وَالطَّسْتُ تَحْتَهَا وَهْىَ تُصَلِّي  

One of the mothers of the faithful believers (i.e. the wives of the Prophet ﷺ ) did Iʿtikaf while she was having bleeding in between her periods.  

أَنَّ بَعْضَ أُمَّهَاتِ الْمُؤْمِنِينَ اعْتَكَفَتْ وَهْىَ مُسْتَحَاضَةٌ