All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Shaykh Ibn ‘Uthaymeen said: "If this discharge is among the preliminary signs of menstruation, it is considered menstruation. This is known by the pain and cramps that accompany menstruation. When the brownish discharge that follows menstruation occurs, the woman should wait until it stops as the brownish discharge that comes out along with menstruation is considered menstruation. ‘Aa’ishah told women, “You should not be hasty until you see the white discharge (signifying the end).”"
Allaah Knows best.