Charak Samhita
आर्तवे सा विमुक्ते तु तत्क्षणं लभते सुखम् । रजसो गमनादूर्ध्वं ज्ञेयोदावर्तिनी बुधैः ॥२६॥
After discharge of menstrual blood, pain subsides. It is known by the wise physician as udavartini because of the upward course of menstrual blood.
english translation
Artave sA vimukte tu tatkSaNaM labhate sukham । rajaso gamanAdUrdhvaM jJeyodAvartinI budhaiH ॥26॥
hk transliteration by Sanscript