Body & health

Uterus

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Not yet reviewed by a clinician. This health entry was written from the public-health sources listed below and is general information only. It is not medical advice.

Definition

The uterus, or womb, is a hollow, muscular organ in the pelvis where a fertilised egg can implant and a pregnancy develops. Its lining is shed each month as a period when there is no pregnancy.

At a glance

  • The uterus, or womb, is a hollow, muscular organ in the pelvis where a pregnancy develops.
  • When not pregnant, it is roughly the size and shape of an upside-down pear.
  • Its lining, the endometrium, thickens each cycle and is shed as a period if there is no pregnancy.
  • Contractions of its muscular wall cause labour and are one cause of period cramps.
  • Persistent heavy bleeding or pelvic pain should be discussed with a clinician.

In detail

The uterus is roughly the size and shape of an upside-down pear when not pregnant. Its inner lining, the endometrium, thickens during each menstrual cycle under the influence of hormones. If no pregnancy occurs, the lining breaks down and leaves the body through the cervix and vagina as menstruation.

The muscular wall of the uterus can stretch greatly during pregnancy and contracts during labour and during periods, which is one cause of period cramps. Conditions affecting the uterus include fibroids, endometriosis-related problems and adenomyosis; persistent heavy bleeding or pelvic pain should be discussed with a clinician.

In a sentence

  • The ultrasound report said the uterus looked a normal size.
  • My friend explained that her cramps come from the uterus contracting during her period.

Where the word comes from

From Latin uterus, meaning womb or belly. Womb is the older everyday English word for the same organ.

Common questions

Are the uterus and the womb the same thing?

Yes. Uterus is the medical term and womb is the everyday English word. Both describe the hollow, muscular organ where a fertilised egg can implant and a pregnancy develops.

Why do periods cause cramps?

The muscular wall of the uterus contracts to help shed its lining during a period, and these contractions can be felt as cramps. Mild cramps are common, but pain that stops you from doing everyday things, or very heavy bleeding, is worth discussing with a doctor, as it can point to conditions such as endometriosis or fibroids.

Related terms

Sources

  1. MedlinePlusUterine Diseases
  2. Planned ParenthoodWhat are the parts of the female sexual anatomy?