The Onset of the Niddah Status
A woman usually becomes niddah through menstruation or other uterine bleeding. She can also become niddah without bleeding if her uterus is opened during a medical procedure, or if she claims to be niddah. A woman who gives birth (yoledet) or who marries for the first time (dam betulim) must observe similar laws to a niddah.
A woman who discovers an apparent bloodstain on her clothing or another surface may be niddah as well. The halacha in such cases may depend on whether or not she felt a hargashah. If she did, then she is considered niddah; if not, then her status depends on several factors (see ketamim). Therefore, a woman who finds an unexpected bloodstain should not independently assume that she is niddah, but should consult a rabbi. Until her status has been clarified, however, she should follow all the laws of niddah.
Bleeding that is caused by a wound, or whose source is not in the uterus, does not render a woman niddah. However, the cause of bleeding is often difficult to determine with certainty, and a rabbi should be consulted in such cases.
