Menstruation is your body’s process of shedding the lining of your uterus about every 28 days. This resets your body to prepare for the next month’s possibility of pregnancy.
Medically reviewed by Holly Almond, RN, BSN.
Why it matters: Understanding the menstruation phase of your menstrual cycle helps you prevent pregnancy, prepare for pregnancy, and track your overall health.
What happens during menstruation?
Your uterus sheds its lining through your vagina over the course of your period, which usually lasts about 3-7 days.
What is menstrual blood?
Menstrual blood is made up of blood and tissue from the lining of your uterus. This blood flows through your cervix to be expelled through your vagina.
What causes menstruation to happen?
Your pituitary gland and your ovaries make hormones (chemical messengers) at certain times in your cycle that trigger menstruation.
- Follicular: These hormones tell your uterus to thicken its lining so that the possible fertilized egg could implant.
- Ovulation: Your hormones trigger your ovary to release an egg, which travels into the fallopian tube and waits for sperm to fertilize it. If your egg remains unfertilized, it breaks down, and pregnancy does not occur.
- Luteal: Progesterone (hormone) levels increase to support a possible pregnancy. If pregnancy does not occur, progesterone and estrogen levels will drop before menstruation.
- Menstruation: The uterine lining breaks down and is expelled through your vagina.
Adrienne Bergmeier
Adrienne Bergmeier is a Communications Coordinator at The Pregnancy Network.