Abnormalities of the uterus

What are abnormalities of the uterus?

Your uterus (womb) is a pear-shaped organ, tucked away in your pelvis. A normal uterus is about 7.5cm long, 5cm wide and 2.5cm deep. Inside, it is hollow with thick muscular walls. The lower part of the uterus dips down into the vagina and is called the cervix. The upper portion is called the fundus and this is where the fertilized egg grows into a baby.

A small number of women has a uterus (womb) that differs in shape or structure from the norm. This is called an abnormality of the uterus, or a uterine abnormality. It is a bit of a catch-all phrase, and the figures reflect this. Between one woman in 100 and one woman in 30 has a uterine abnormality (Nahra-Lynch and Toffle 1997).

It's also difficult to know how many women have an abnormality, because it's possible to have one without knowing it.

Will I be able to have a baby if I have an abnormal uterus?

Generally speaking, uterine abnormalities do not affect your ability to become pregnant and give birth. However, depending on the abnormality, it may make it more difficult for you to carry your baby for the full nine months of pregnancy. This may mean you need extra monitoring. It is possible to have a baby if you have one of the following uterine abnormalities:

Uterus didelphysUterus didelphys This is an extremely rare abnormality where the uterus has two inner cavities. Each cavity may lead to its own cervix and vagina. This means there are two cervixes and two vaginas.

Unicornuate uterusUnicornuate uterus
A unicornuate uterus is half the size of a normal uterus and there is only one fallopian tube. Because of its shape, it is described as a uterus with one horn. It is a very rare abnormality. It develops in the earliest stages of life, when the tissue that forms the uterus does not grow properly. If you have a unicornuate uterus, you probably have two ovaries. Only one will be connected to your uterus, though.

Bicornuate uterusBicornuate uterus
Instead of the womb being pear-shaped, this type of uterus is looks more like a heart, with a deep indentation at the top. It is called a uterus with two horns, because of its shape. It's thought that about 20 per cent of women with uterine abnormalities have a bicornuate uterus (Lin 2004).

Septate uterusSeptate uterus
This is where the inside of the uterus is divided by a muscular or fibrous wall, called the septum. A 3D ultrasound or an MRI will confirm the presence of the septum. The septum may extend only part way into the uterus (partial septate uterus) or it may reach as far as the cervix (complete septate uterus). Partial septates, affecting about 33 per cent of women with abnormalities, are more common than complete septates.

Arcuate uterusArcuate uterus
This looks more like a normal uterus, except it has a dip, or slight indentation at the top.

How will having an abnormal uterus affect my pregnancy?

It really depends on the extent of the abnormality. For example, if you have a septate uterus, unfortunately, it may mean you are at greater risk of having a miscarriage (Lin 2004). If you have a septate uterus, you can have treatment to correct the abnormality before you conceive. If your uterus differs only slightly from the norm, you're no more likely than anyone else to have a miscarriage.

There may be a greater chance of you having complications during your pregnancy. Again, it depends on what type of abnormality you have. If you have a unicornate uterus, you are more likely to have complications during pregnancy or birth (Lin 2004).

Your baby may not settle into the usual head-down position if your uterus is an unusual shape. He may get into a bottom-down, breech position, or a crossways, tranverse position. This may happen if you have a bicornuate uterus. You will be offered a caesarean section, because this is thought to be the safest way for your baby to be born (Baker 2006).

If you have a unicornuate or bicornuate uterus, it is perfectly possible to have a successful pregnancy. However, your waters may break early and you may go into premature labour (RCOG 2004).This is because there comes a point where there simply isn't enough room for your baby to grow any more. Over-stretching of your uterus triggers labour.

Another reason you may have your baby early is to do with your cervix, or the neck of your uterus. It may not be strong enough to keep your baby inside, leading it to open too early. This is called a weak cervix. It tends to be a problem for women with an abnormally shaped uterus who are expecting their first baby. The more pregnancies you have, the less of a problem it is.

How can I cope when I am pregnant?

If you know that you have an abnormally shaped uterus, you may feel very anxious during your pregnancy. This may especially be the case if you have had previous miscarriages. It's best to go to all your prenatal appointments, because your midwife and obstetrician will want to keep a close eye on you.

Try to stay as relaxed as possible and keep busy to distract yourself. Ask your midwife or doctor to explain clearly to you the signs of premature labour. Then if your baby starts coming too soon, you will know what is happening and can get to hospital quickly.

If at any time you feel that something is wrong, contact your doctor or midwife immediately. You can also go to triage at your local hospital’s maternity floor. Don't worry about raising a false alarm. Your midwife, doctor, or nurse will be only too pleased to check you over and reassure you.

Reviewed for Canada by Suzanne Wong, MD

Last reviewed September 2012


Baker PN. 2006. ed. Obstetrics by ten teachers 11:128. Hodder Arnold: London

Lin, PC. 2004. Reproductive Outcomes in Women with Uterine Anomalies. Journal of Women's Health. 13(1):33-39

Nahra-Lynch M, Toffle RC. 1997. Multiple gestation in a unicornuate uterus: a case report. Journal of Reproductive Medicine 42:451-454

RCOG. 2004. Couples with recurrent miscarriage: what the RCOG guideline means for you. Royal College of Obstetricians and Gynaecologists. [accessed February 2010]

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