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What Is Considered a Small Uterus?

Marlene de Wilde
Marlene de Wilde

While there is no exact definition of a small uterus, one that is about 25% smaller than average should still be able to support a pregnancy. The average uterus is 3 inches (7.5 cm) long, 2 inches (5 cm) wide, and 1 inch (2.5 cm) deep. Symptoms of a small uterus include irregular or no periods and abdominal pain. However, many women are unaware of uterine abnormalities as there may be no symptoms at all.

A healthy uterus is pear-shaped, hollow, and lined with thick muscular walls. There are two fallopian tubes, each connected to an ovary filled with eggs entering the uterus on either side at the top. A uterus that differs in structure from the norm is considered an abnormality which may or may not lead to difficulties in conception and pregnancy.  The uterus, normal-sized or smaller than average, stretches and grows when stimulated by the hormones released during pregnancy. It is only when the size is an indication of other conditions that a small uterus may lead to problems.

What Medical Conditions Are Associated With a Small Uterus?

A small uterus, also known as uterine hypoplasia or hypoplastic uterus, is a congenital condition. Congenital disorders are those which are present in the child from birth. The causes of this abnormality are still unknown.

The process of development of the female reproductive system begins in the embryo with the primordial Mullerian ducts. These are paired ducts that differentiate to form the fallopian tubes, uterus, and vagina in the female child. 

Mayer-Rokitansky-Küster-Hauser Syndrome

Symptoms of a small uterus may include irregular or no periods.
Symptoms of a small uterus may include irregular or no periods.

A Mullerian duct anomaly is a very rare condition affecting one in every 4,500 newborn girls, called uterine agenesis or Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. Uterine agenesis results in a very small uterus or none at all and is usually present with vaginal agenesis, which is the lack of or incomplete vagina. 

Girls born with a small uterus or MRKH syndrome have a typical chromosome pattern, with 46 chromosomes and an XX pairing. Therefore, the abnormality is only physical. However, their ovaries will function normally, and their genitalia will appear normal externally. Also, their breast and pubic hair will develop as usual.  

A small uterus may be diagnosed via an ultrasound.
A small uterus may be diagnosed via an ultrasound.

There are two types of MRKH syndrome. In type 1, only the reproductive organs are impacted by the abovementioned effects. In type 2, other organs (aside from the reproductive ones) can also develop abnormally. For example, a person with MRKH syndrome type 2 might have abnormally formed, positioned, or undeveloped kidneys, skeleton abnormalities, or hearing and heart defects. 

No matter the size of the uterus prior to pregnancy, it stretches and grows during pregnancy.
No matter the size of the uterus prior to pregnancy, it stretches and grows during pregnancy.

Women who are born with this condition might not begin menstruating during puberty. This abnormality can also prevent conception or pregnancy, as mentioned previously. In this case, surrogacy is nearly always the only solution for women to have a child.

Unicornuate Uterus

Another Mullerian duct anomaly leads to a unicornuate uterus. This is generally only half the size of a normal uterus, and there is only one fallopian tube instead of two. As long as this is healthy and developed, then it should be possible for the woman to conceive, but she will need careful monitoring during the pregnancy and birth as having a unicornuate uterus significantly increases the risk of pregnancy loss and preterm labor.

Symptoms of a small uterus may include abdominal pain.
Symptoms of a small uterus may include abdominal pain.

There are many ways of diagnosing a small uterus. The most common test used first is that of the 2D ultrasound scan, which is the one used by most gynecologists or obstetricians. This is enough to indicate that there is a problem, but the images are not usually sharp enough for a diagnosis. Further tests include 3D ultrasound scan, magnetic resonance imaging (MRI), or a minor operation called a laparoscopy.

How Does a Typical Uterus Work During Pregnancy?

An MRI scan may be useful in diagnosing a small uterus.
An MRI scan may be useful in diagnosing a small uterus.

The primary function of the uterus during pregnancy is to house and nurture the growing fetus. This organ, lined with muscular walls, has three parts. It is comprised of the fundus (the top of the uterus), the corpus (the main body), and the cervix (the lower region of the uterus). There is also a part connecting the corpus to the cervix: the isthmus. At the isthmus, the uterus starts to narrow between the corpus and cervix.

The fundus functions as the opening of the uterus. It leads into the corpus, where the fetus grows during pregnancy. The corpus expands during pregnancy to hold the baby. The cervix is a cylindrical tissue at the very bottom of the uterus, connecting the uterus and vagina. The baby is pushed through here during labor.

A uterus that has never been pregnant before is typically around 2.5 - 3 inches (about 7 cm) long. On the other hand, a uterus that is not currently pregnant but has been pregnant previously is typically around 3.5 inches (about 9 cm). The uterus can stretch dramatically throughout pregnancy to accommodate the growing baby's size.

The uterus also plays an important role when a woman goes into labor. Contractions arise when the uterus' muscles contract to push the baby into the birth canal. These muscles in the uterus deliver the baby out of the womb and into the world.

After the labor is over and the baby is delivered, the uterus contracts once more to push the placenta out. The muscles stay contracted to prevent hemorrhage (severe bleeding).

How Does the Uterus Work During Menstruation?

The lining of the uterus is called the endometrium, and this lining sheds during menstruation. The endometrial lining changes in size each month as the body prepares to ovulate, ovulate, and then menstruate.

As the body gets closer to ovulation (the process where the ovaries release an egg), the endometrial lining gets thicker to prepare for the possibility of housing a fetus. When this egg is not fertilized, the uterus sheds its endometrial lining, causing menstruation.

Can a Small Uterus Be Treated?

In some cases, surgery can correct abnormal uteruses. However, surgery is a more feasible and likely solution for other uterus conditions, such as the septate uterus. This condition is when the uterus is divided into two regions by a membrane called the septum. 

In those cases where the uterus is unicornuate or only 25% smaller than average, any possible pregnancy must be carefully monitored. However, in many cases, women with a small or underdeveloped uterus must find alternative plans for pregnancy. 

Surrogacy is one alternative option. In this process, one woman agrees to carry a baby for another woman or couple, often for a sum of money. Surrogate mothers are impregnated through In Vitro Fertilization (IVF). IVF is the procedure in which sperm is used to fertilize an egg in a laboratory dish before being inserted into the uterus.

Final Thoughts

As we mentioned earlier, a small uterus is a rare condition. For this reason, it is essential that patients who suffer from it have access to adequate information and support to overcome the difficulties this disorder may present.

Discussion Comments

anon991845

There really seems to be no correlation between the size of the woman to the size of the uterus. I'm 5' 10", 170 lbs (pretty tall/big woman), and my uterus is only 5 cm in length. I can't even use an IUD because of that.

difuse

I'm 23 and have never had a period. The doctor told me that the size of my uterus is very small. I want to know if there is any way to increase its size.

amypollick

@anon315374: Sounds like you need another OB/GYN, preferably one who specializes in high risk pregnancies. With one miscarriage and two stillbirths, it sounds like you need the kind of unique care only a high-risk specialist provides. If there is a teaching hospital in your area, they should have a high-risk doctor on staff. Good luck.

anon315374

I have questions on if my uterus is too small. I am 23 years old. My pregnancy history includes a miscarriage at 8 weeks in 2007, my son was stillborn at 34 weeks in 2011, and my daughter was stillborn at 33 weeks in 2012. I have no idea what could be causing this problem.

One doctor said "maybe" my uterus is small. It makes me so mad because my doctors seem to have put my daughter's death in the past. I've been trying to find answers on my own. I know I will only get so far, and I will need my doc's help at some point, but until then I guess I'll look for answers myself.

anon271333

I'm 22 years old and my problem is that my uterus size is small. I want to know if a cure for a small uterus is possible?

SZapper

I just wanted to say that I agree with this article. There's pretty much no way of knowing about any internal abnormalities until a doctor tells you. Anyone reading this could have a small uterus (well, unless you're a man.)

As far as I know, my uterus is the regular size. However, a doctor told me quite awhile ago that I have a retroverted uterus. Apparently it faces the opposite direction than usual. What's interesting is that my doctor told me 1 in 5 women have this!

If my doctor hadn't told me that, I never would have known! I mean, how could I have?

ElizaBennett

@Kat919 - If you think about it, you'll realize that the uterus is remarkably elastic. I have no medical knowledge about small uteri, but think about what a regular one does - it increases from the size of like an apple or even smaller to the size of a watermelon! So it's awfully elastic.

And when people are carrying multiples, it can get even bigger - but then there's a higher risk of pregnancy loss or preterm birth, increasing as the number of babies goes up. So maybe there's an analogy there.

I guess you lost touch with your friend, but I'm curious what she decided. I hope she found a way to be at peace with her situation one way or another, whether by taking her chances, by adoption or surrogacy, or by embracing a child-free life. My babies have been the great joy of my life and my heart aches for anyone who wants them and cannot have them.

Kat919

How could a person with a small uterus be able to carry a baby to term? I mean, babies get pretty big at the end there. I had a friend in college years back who happened to mention that she actually had two small uteri (both, I assume, unicornuate) and that it might mean she would have trouble having children. She mentioned the risk of preterm labor or miscarriage and she wasn't sure she wanted to try having kids at all; she said it would just be too heartbreaking if she kept losing babies.

I don't know the specifics of her situation, but it made the title of this article catch my eye. How is it that you do not need a full-size uterus?

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    • Symptoms of a small uterus may include irregular or no periods.
      By: Eskymaks
      Symptoms of a small uterus may include irregular or no periods.
    • A small uterus may be diagnosed via an ultrasound.
      By: JackF
      A small uterus may be diagnosed via an ultrasound.
    • No matter the size of the uterus prior to pregnancy, it stretches and grows during pregnancy.
      By: Patricia Hofmeester
      No matter the size of the uterus prior to pregnancy, it stretches and grows during pregnancy.
    • Symptoms of a small uterus may include abdominal pain.
      By: staras
      Symptoms of a small uterus may include abdominal pain.
    • An MRI scan may be useful in diagnosing a small uterus.
      By: EPSTOCK
      An MRI scan may be useful in diagnosing a small uterus.