'That is not menstruation, rather it is a kick [1] in the womb, so let her work out the length of the menses that she used to have, and stop praying (for that period of tie), then after that period of time), then after that let her perform Ghusl for every prayer.'" [1] A kick in the womb: in other narrations means "A kick from Shaitan,", meaning that the Shaitan uses it to confuse her about her religious commitment. (Using translation from Nasāʾī 209)
شَأْنُهَا لِرَسُولِ اللهِ ﷺ فَقَالَ لَيْسَتْ بِالْحَيْضَةِ وَلَكِنَّهَا رَكْضَةٌ مِنَ الرَّحِمِ فَلْتَنْظُرْ قَدْرَ قُرْئِهَا الَّتِي كَانَتْ تَحِيضُ لَهُ فَلْتَتْرُكِ الصَّلَاةَ ثُمَّ لِتَنْظُرْ مَا بَعْدَ ذَلِكَ فَلْتَغْتَسِلْ عِنْدَ كُلِّ صَلَاةٍ وَلْتُصَلِّ