As you get older, your body goes through a transition. Your ovaries produce less of the hormones estrogen and progesterone. Without these hormones, your periods become more erratic and eventually stop.

Once you’ve been without a period for 12 months, you’re officially in menopause. The average age when American women go into menopause is 51. The physical changes that usher in menopause can begin as early as age 40, or may not start until your late 50s.

One way to predict when you’ll start menopause is to ask your mother. It’s typical for women to start menopause at roughly the same age as their mother and sisters. Smoking can accelerate the transition by about two years.

Here’s a look at menopause through the ages, and what types of symptoms to expect as you reach each milestone.

A couple of missed periods when you’re 40 might lead you to think you’re pregnant, but it’s also possible to begin menopause at this age. About 5 percent of women go into early menopause, experiencing symptoms between the ages of 40 and 45. One percent of women go into premature menopause before age 40.

Early menopause can occur naturally. Or, it may be triggered by surgery to remove your ovaries, cancer treatments such as radiation or chemotherapy, or autoimmune diseases.

Signs you’re in early menopause include:

  • missing more than three periods in a row
  • heavier or lighter than usual periods
  • trouble sleeping
  • weight gain
  • hot flashes
  • vaginal dryness

Because these can also be symptoms of pregnancy or other medical conditions, have your doctor check them out. If you’re in early menopause, hormone therapy can help alleviate hot flashes, vaginal dryness, and other menopausal symptoms.

Going into menopause early could prevent you from starting a family if you’ve been waiting. You may want to consider options like freezing your remaining eggs or using donor eggs to conceive.

Many women enter the perimenopausal phase in their late 40s. Perimenopause means “around menopause.” At this stage, your estrogen and progesterone production slows, and you begin to make the transition into menopause.

Perimenopause can last for 8 to 10 years. You’ll likely still get a period during this time, but your menstrual cycles will become more erratic.

During the last year or two of perimenopause, you may skip periods. The periods you do get could be heavier or lighter than usual.

Symptoms of perimenopause are due to rising and falling estrogen levels in your body. You can experience:

  • hot flashes
  • mood swings
  • night sweats
  • vaginal dryness
  • difficulty sleeping
  • vaginal dryness
  • changes in sex drive
  • trouble concentrating
  • hair loss
  • fast heart rate
  • urinary problems

It’s harder to get pregnant during perimenopause, but not impossible. If you don’t want to conceive, continue to use protection during this time.

During your early 50s, you may be either in menopause, or making the final transition into this phase. At this point, your ovaries are no longer releasing eggs or making much estrogen.

The change from perimenopause to menopause can take one to three years. Symptoms like hot flashes, vaginal dryness, and sleeping difficulties are common during this time. If you experience these symptoms, talk to your doctor about hormone therapy and other treatments to relieve them.

By age 55, most women have gone through menopause. Once a full year has passed since your last period, you’re officially in the postmenopausal phase.

You may still have some of the same symptoms you experienced during perimenopause and menopause, including:

  • hot flashes
  • night sweats
  • mood changes
  • vaginal dryness
  • difficulty sleeping
  • irritability and other mood changes
  • urinary problems

In the postmenopausal stage, your risk for heart disease and osteoporosis increases. Talk to your doctor about making healthy life changes to protect yourself against these conditions.

A small percentage of women are late going into menopause. This isn’t necessarily a bad thing.

Studies have linked late menopause to a lower risk of heart disease, heart attack, stroke, and osteoporosis. It’s also linked to a longer life expectancy. Researchers believe that prolonged exposure to estrogen protects the heart and bones.

If you’ve already been through menopause, it doesn’t always mean you’re done with its symptoms. An estimated 40 percent of women ages 60 to 65 still get hot flashes.

In most women who get hot flashes later in life, they’re infrequent. Yet some women have hot flashes often enough to be bothersome. If you still get hot flashes or other symptoms of menopause, talk to your doctor about hormone therapy and other treatments.

The transition to menopause begins and ends at different times for each woman. Factors like your family history and whether you smoke can make the timing earlier or later.

Your symptoms should serve as a guide. Hot flashes, night sweats, vaginal dryness, and mood changes are all common at this time of life.

If you think you’re in perimenopause or menopause, see your gynecologist or primary care provider. A simple test can tell you for sure based on hormone levels in your blood.