A young woman’s first period gets a lot of attention.

There are books upon books about how it works, what it feels like and how to manage it. Some people even throw their daughters a party to celebrate the special day.

There’s another major change in a woman’s reproductive cycle that doesn’t get quite as much attention. Unfortunately, it often comes as an unpleasant surprise when symptoms begin to appear.

It’s not menopause — that’s the end game. It’s perimenopause.

Perimenopause is the stretch of time before menopause begins where a woman’s body begins to transition into the next phase. It can last from four to eight years and typically begins in a woman’s 40s.

“During the 40s, the ovaries begin to make varying amounts of estrogen and progesterone. This fluctuation can lead to significant changes in the menstrual cycle, including going months without a period or having a shorter cycle, and changes in how heavy someone’s flow is,” said Therese Hughes, MD, an obstetrician and gynecologist with Endeavor Health.

Gradually, the length of time between periods increases until the period stops altogether. You’re officially in menopause once you’ve gone 12 months in a row without a period. The average age that happens is 51 but it can happen anytime between 40 and 58.

How can someone tell if they’re in perimenopause?

They may experience some of the following common symptoms in the years leading up to menopause:

  • Menstrual cycle changes. Your cycles will likely differ widely before they stop. You may have periods that are longer, shorter, heavier or lighter than usual, or you may begin to skip periods.
  • Hot flashes. A hot flash feels like a sudden sensation of heat that often starts at your head and face and spreads to the rest of your body, causing you to break a sweat. Hot flashes usually last from a few seconds to several minutes and can happen multiple times per day or only a few times a month.
  • Sleep problems. This is a classic symptom of perimenopause. You may have trouble falling asleep, you may wake up earlier than usual, and/or you may have night sweats — hot flashes that wake you up while sleeping.
  • Vaginal dryness. As estrogen levels decrease, the lining of the vagina may become thinner, dry and less elastic. This can make sex uncomfortable for some women. Ask your doctor about water-based lubricants, vaginal estrogen or other options.
  • Urinary issues. The urethra can also become dry, inflamed or irritated, which increases the risk of urinary tract infections.
  • Emotional changes. Sudden shifts in hormones may cause mood swings, anxiety, irritability, depression and forgetfulness.
  • Difficulty losing weight. Weight gain is not inevitable, it’s just more difficult to prevent. As your metabolism slows down and fat storage in your body redistributes, it can be more difficult to control your weight (especially around your waist). But it can be done! A proper diet, portion control and regular exercise helps.

Although each women experiences menopause differently, symptoms usually decrease in severity and frequency over time and eventually stop after you reach menopause.

In the thick of perimenopause, some women find relief from symptoms through menopausal hormone therapy. Hormone therapy can be very effective, but also carries some risks and side effects. Talk to your doctor about whether you’re a good candidate for hormone therapy.