Periods are changes that many girls see at puberty. You’ve probably heard of menstruation before—commonly called “periods.” 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.
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 )
It just depends on your 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