When guys have the urge to have sex during their girlfriend's period, the most common response they get is: "Are you asking for it?!" followed by a beating...

Making love during menstruation
What are the effects on the body?
1. Prolonged menstrual period
Because of the excitement of both partners, the woman's genitals become congested with blood, resulting in increased menstrual flow and her period lasting a few more days.
2. Affects fertility
Menstrual periods are not a naturally "safe period"; they are the most likely time for ectopic pregnancies to occur.
3. Causes infection
Having sex during menstruation can introduce bacteria from the outside into the vagina, or push bacteria from the vagina into the uterine cavity, potentially leading to cervicitis, pelvic inflammatory disease, and urethritis.
So, just in case, let's all take it easy. Aren't twenty-odd days a month enough?