Menstrual Periods
حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا مُعْتَمِرٌ، عَنْ خَالِدٍ، عَنْ عِكْرِمَةَ، عَنْ عَائِشَةَ، أَنَّ بَعْضَ، أُمَّهَاتِ الْمُؤْمِنِينَ اعْتَكَفَتْ وَهْىَ مُسْتَحَاضَةٌ.Narrated `Aisha:One of the mothers of the faithful believers (i.e. the wives of the Prophet (ﷺ) ) did I`tikaf while she was having bleeding in between her periods
From Sahih al-Bukhari, whose reports the scholars accept as authentic.