Parashat Acharei Mot
The Torah and the Mishnah, in their laws of female uterine bleeding, maintain a strong separation between the normal (niddah) and the pathological (zavah), with different criteria for triggering different periods of abstinence. But somewhere in early Amoraic Babylonia, these boundaries begin to blur, and normal menstruation is treated more and more similar to pathological bleeding. Why is this? And why is this stringent regime still so entrenched today?