Having periods – also called menstruation, is a change that many girls will experience at puberty. It usually happens when a gonad called an ovary sends an egg down to the womb (called the ‘uterus’) to be fertilized (joined with a sperm). If it isn’t fertilized, the blood lining of the uterus is shed (that is a period). The blood leaves the uterus and goes through the cervix (a tiny hole at the base of a womb (a.k.a. uterus) that leads to the vagina. The blood will then come out of the vaginal opening. Most periods usually last between 3-7 days. Some people with periods will feel some pain just before their period arrives, and during the first day, others will not feel anything more than the blood itself.
There are plenty of resources that talk about what periods are and what they feel like. We recommend this bbc page, and the book The Care and Keeping of You 2 from American Girl.
Periods: What about you?
Girls WITHOUT a Y chromosome may have periods if they have a womb (uterus).
Most girls WITH a Y chromosome won’t have periods at puberty since there is no womb (a.k.a. uterus) or ovary. Some girls with Y might have period someday, if there is a small womb present that grows with hormones (this may happen for some with Swyer’s Syndrome or with ovotestes.)
This all just depends on your individual body. Talk more about this with your parents and your doctor.
For more information about gonads, eggs, sperm, and making babies, click here. For more on not having a period and talking with friends, click here.