If you’re a pre-teen or teen girl who has not yet had a menstrual period, you may be wondering when your first period will start. And you may be feeling nervous about it.
If you’re very worried, try to talk to your mom or another female relative. If you’d rather not speak to a family member you could try talking to a female teacher or school counsellor.
The first period, known as menarche (pronounced men-ar-kee, a Greek word for "beginning") can occur as early as 8 years old or as late as 15 or 16.
If you haven’t started your period when you are over 16, you should see a doctor. The average age for a girl to start her period in the U.S. and the U.K. is 12 years.
A period is a healthy sign that your body is capable of carrying a baby, should you decide to become a mother at some point in your future.
Why does a Period Happen?
You have two ovaries which have follicles in them that contain immature eggs. Your pituitary gland (a gland in your brain) releases a hormone called follicle stimulating hormone (FSH) and this causes the eggs to grow.
While your eggs are maturing in these follicles, your body also produces a hormone called estrogen. This signals to your uterus to grow a thick cushion-like lining made of blood and tissue.
If you were to get pregnant, this special lining would be the perfect environment for a fertilized embryo (baby in very early stages) to develop.
Once your eggs have grown big enough to be fertilized by a sperm, the rising levels of estrogen cause the pituitary gland to release a large amount of luteinizing hormone (LH) known as the LH surge and this signals to the ovary to release an egg.
The follicle bursts and an egg is ejected into the fallopian tube where it travels to the uterus to be fertilized by a sperm. This is called ovulation.
The empty follicle produces another hormone called progesterone which will help maintain pregnancy if the egg is fertilized and prevents further ovulation from occurring.
If however, no fertilization takes place after a few days, the empty follicle stops producing progesterone and gets re-absorbed into the ovary.