The Niddah Status
A woman enters the niddah status when she experiences uterine bleeding not due to trauma. While the most common cause of this status is menstruation, niddah and menstruation are not completely synonymous. For example, opening of the uterus beyond a certain minimum size renders a woman niddah even in the absence of visible bleeding. Uterine bleeding from the withdrawal of hormones (such as occurs when using oral contraceptive pills), and as side effects of medication also causes the onset of the niddah status.