No one can say exactly when you'll get your first menstrual period, but you will get it sometime during puberty. Puberty is the time in your life when you begin to become an adult. This means a lot of growing and changing — both inside and out.

Some girls start puberty at age 8, and others may start as late as 13 or 14. Each girl goes at her own pace. So don't think you're weird if you start puberty a little earlier or a little later than your friends.

At the beginning of puberty, you'll notice that your breasts are developing and hair will start to grow on your genitals (pubic hair). A little later, hair also will grow under your arms.

For most girls, their first menstrual period, or menarche (say: meh-nar-kee), begins about 2 to 2½ years after breast development starts. Some girls may get their period in less than 2 years. For other girls, it may take longer. Every girl is different, and there is a wide range of normal development during puberty.

A good sign you're getting close to the time when your first period will arrive is if you notice a thick, white mucous discharge coming from your vagina. Usually, this happens about 6 months before you get your first period.

You Could Be a Mom Someday

Menstruation is a signal that a girl's body has changed so that someday she could have a baby. Every girl has two ovaries filled with thousands of tiny eggs and two fallopian tubes that connect the ovaries to a place called the uterus or womb, where babies grow.

If you've already gotten your period, it means that special chemicals, or hormones, in your body are telling the eggs in your ovaries to mature. So each month, the ovary releases one mature egg that begins its journey to the uterus.

Between periods, the walls of your uterus get thicker with blood and tissue, which can act as a nice, soft cushion for a baby. Once the egg reaches the uterus, if it hasn't been fertilized by sperm, the uterus doesn't need this blood-and-tissue cushion and it leaves through the vagina. Ta dah! Your period has arrived!

Some girls wonder if their periods are normal. No two girls' periods are exactly alike. Periods can last from 2 days to a week. Some girls have very heavy periods with monthly cramps, and others have much lighter periods after the first couple of days.

It also takes a while (usually 12 to 18 months) for a girl's period to become regular after her first period. You may get your first period and then not have another for a few months. As you get older, your cycle will become more regular — usually between 21 and 34 days in length.

The amount of blood you lose during your period can vary, too. It can seem like a lot, but typically it's only about 2 tablespoons. Call the doctor if you think that you are bleeding too much or you go 3 months without getting your period.

Are you thinking a lot about when your first period will arrive? You're not alone. Lots of girls wonder and wonder — when will it come? If you feel a little worried or anxious about getting your period, it can help to talk to someone you trust, like your mom or older sister.

Reviewed by: Mary L. Gavin, MD
Date reviewed: September 2011