Menstrual flow Blood and discharge that are passed out of the uterus through the vagina during the beginning of the menstrual cycle. Related Articles: Glossary: Menstrual cupGlossary: Sanitary padBehavior, Fertility, & More | Breaking Down the Menstrual CycleMany, many factors contribute to a woman’s behavior, sex drive, and whom she chooses to sleep with. Yet, when Day 12 comes around and you find yourself choosing that short skirt, you’ll know why. Sasha Co- Founder of Psych n Sex, previous writer and campus educator for the Kinsey Institute & published psychology researcher. Manhattan girl obsessed with post ww2 abstract expressionism, beet juice, vintage clothing & Scandinavia.