The cervix is the doorway between your vagina and uterus. It’s the bottom part of your uterus located at the very top of your vagina and looks kind of like a small doughnut. The opening in the center of the cervix is called the os.

The cervix works like a gatekeeper, controlling what is and isn’t allowed through the os.

When you aren’t pregnant, your cervix produces mucus, known as vaginal discharge. During most of the month, your cervix produces a thick mucus that clogs up the os, making it difficult for sperm to enter your uterus.

When you ovulate, however, your cervix produces a thin, slippery mucus. Your cervix may also soften or change position, and the os may open slightly. This is all a calculated effort to make it easier for sperm to enter your uterus.

In the days before your period begins, your cervix may harden or change position. The os may narrow and prepare to close in the event of a pregnancy. If there isn’t a pregnancy, the cervix will relax and the os will open to allow the lining of your uterus to exit your body through your vagina.

A closed cervix can sometimes happen temporarily during part of each menstrual cycle. Other times, the cervix may always seem to be closed. This is known as cervical stenosis. It happens when the os becomes unusually narrow or completely blocked off. Some women are born with cervical stenosis, but others develop it later on.

Depending on your age and whether or not you’re trying to become pregnant, you might not have any symptoms of a closed cervix or cervical stenosis.

If you haven’t gone through menopause, you might notice your periods becoming more irregular or painful. A closed cervix can also cause infertility because sperm can’t travel into the uterus to fertilize an egg.

If you’ve already gone through menopause, you might not have any symptoms. But complications can cause abdominal pain. You may also feel a lump in your pelvic area.

While you can be born with a closed cervix, it’s more likely to be triggered by something else.

Possible causes include:

To diagnose a closed cervix, your gynecologist will need to perform a pelvic examination with a tool called a speculum. They’ll insert the speculum into your vagina, allowing them to see your cervix. They’ll carefully examine its size, color, and texture. They may also look for any cysts, polyps, or other signs of anything unusual.

If your os looks narrow or otherwise appears abnormal they may try to pass a probe through it. If they can’t, you may get a diagnosis of cervical stenosis.

Treatment for a closed cervix depends on a number of factors, including:

  • your age
  • whether or not you plant to have children
  • your symptoms

If you don’t plan to have children and aren’t having any symptoms, you likely won’t need treatment.

But if you’re trying to get pregnant or have painful symptoms, your doctor may recommend using cervical dilators. These are small devices placed in the cervix. They slowly expand over time, stretching your cervix.

Having cervical stenosis can lead to several complications, including:

  • infertility
  • irregular periods
  • accumulation of fluid

A closed cervix can also lead to hematometra, which happens when menstrual blood builds up in your uterus. This can cause endometriosis, a condition in which uterine tissue grows in places outside the uterus.

Cervical stenosis may also result in a condition called pyometra. Pyometra is an accumulation of pus inside the uterus. If this happens, you’ll feel pain or tenderness in your abdomen.

A closed cervix tends to happen during pregnancy, but it can also happen if you aren’t pregnant. Several things can cause this to happen, so it’s important to follow up with your doctor to figure out the underlying cause.