What is the ruling on intermittent brown and bloody discharge experienced by a pregnant woman in her second month?

If the discharge from a pregnant woman is blood, it is impure (najis) and considered Istihada (non-menstrual vaginal bleeding), because a pregnant woman, according to the preponderant opinion, does not menstruate. However, if it is merely a discharge, then if it originates from the urinary opening, it is impure, but if it originates from the vagina, it is pure. In both cases, it nullifies ablution (wudu').