Uterus During Pregnancy: Sizes And How It Works

check_icon Research-backed

In This Article

When you think of pregnancy, the first thing you may envision is a growing belly. While this is a visible change of pregnancy that is hard to ignore, myriad transformations occur inside a pregnant woman’s body. The most important change is the size of the uterus during pregnancy.

The uterus plays a crucial role in pregnancy as the abode of the infant, and it constantly expands during your gestation journey to hold the developing fetus.

This post discusses interesting details about the uterus, including its size during and before pregnancy, functions, and positions. It also mentions how to maintain a healthy uterus.

Uterus During Pregnancy

The uterus is a distensible organ the size of a closed fist. It grows and changes to become large enough to accommodate a full-term baby. It is held in its position by ligaments, which stretch as the uterus grows.

Dr. Alan Lindemann, MD, a former clinical associate professor at the University of North Dakota, says, “When you get 10 or 12 weeks along, about the end of the third month, your uterus could be appreciably enlarged and feel heavy. You also have more blood supply, so your arteries and veins to and from your uterus might be perceived as heavy.”

Read on as we tell you about what exactly the uterus does, how much its size changes, and how you can measure the organ and keep it healthy.

Size Of Uterus During Pregnancy

As you know, the uterus keeps changing in shape and size as your pregnancy progresses. The uterus expands between 500 and 1,000 times its normal size (1). Let’s see how the organ changes during each trimester.

The first trimester (0 to 12 weeks)

  • At 12 weeks of pregnancy, the size of the uterus remains as small as the size of a grapefruit.
  • As your pregnancy progresses, the uterus grows, putting pressure on the bladder. This is when the frequency of urination increases (2).
  • In the case of twins or multiple pregnancies, the stretching of the uterus will be faster compared to that of a single baby.

The second trimester (14-28 weeks)

  • By the second trimester, the uterus grows to the size of a papaya. The uterus grows upward and develops outside the pelvic area.
  • The uterus expands between the naval area and the breasts and starts putting thrust on the other organs, pushing them away from their original positions (3). This may lead to some tensions in the ligaments and the surrounding muscles, leading to body aches and pains.
  • In some cases, the naval may pop out because of the pressure put by the uterus on other organs.

The third trimester (28-40 weeks)

  • By the third trimester, your uterus will get enlarged to the size of a watermelon. It will move from your pubic brim to the lower bottom of the rib cage.
  • Once you approach labor, your baby will descend into the pelvis.

After childbirth

After childbirth, the uterus shrinks back to its normal position and size. This process is known as involution, which will take about six to eight weeks (4).

Apart from changing in size to accommodate the growing fetus, the uterus also plays other roles during pregnancy.

Functions Of The Uterus During Pregnancy

During pregnancy, the uterus:

  • Accepts the fertilized ovum that passes through the fallopian tube.
  • Creates the placenta for the development of the fetus.
  • Nurtures the fetus with nutrients by developing blood vessels exclusively for this purpose.
  • Contracts to facilitate the exit of the baby and the placenta through the vagina during childbirth.
  • Post-delivery, it shrinks back and starts preparing for the next menstrual cycle.
  • It helps the blood flow into the ovaries. It supports other organs such as the vagina, bladder, and rectum. It plays an important role in sexual functions like triggering orgasm (5).

Interesting how important this inconspicuous organ is, right? Read on, and we will give more information about the uterus and its functions.

How Big Is a Uterus? Normal Size Of A Uterus In Women

The size of the uterus varies from woman to woman. It weighs approximately 70 to 125gm (6). However, the size of the uterus is based on factors such as age and hormonal conditions of a woman.

Size of the uterus:

  • Before attaining puberty, the length of the uterus is about 3.5cm and thickness is approximately 1.4cm (7).
  • After attaining puberty, the length is between 5 and 8cm, width is 3.5cm, and thickness is between 1.5 and 3cm.
  • During pregnancy at term, the uterus measures 38cm in length and 24 to 26cm in width.

Just like the size of the uterus, the position of the uterus also varies from woman to woman. It can be in an anteverted, anteflexed, or any other position.

What Is The Uterus Made Of?

The uterus is an inverted, pear-shaped, and hollow, muscular reproductive organ (8) located in the pelvic region of a woman’s body.

Image: iStock

It is made of smooth muscles lined with various glands. These muscles contract during orgasm, menstruation, and labor, whereas the glands grow thicker with the stimulation of ovarian hormones every month. If you do not become pregnant during the ovulation period, the glands will cast off through the monthly menstrual cycle.

The uterus extends into the vagina through the cervix, which is made up of fibromuscular tissues, and it controls the flow of material into and out of the uterus.

Did you know?
Some women may have a short cervix, which increases the risk of premature labor. Medical or surgical intervention can help prevent complications (15).

Positions Of The Uterus

One of the factors that influence the position of the uterus is the degree of dilation of the bladder. The uterus normally lies right above the bladder and in front of the (anterior) rectum. The normal uterine position is straight and vertical.

Common uterus positions

The uterus position can also be anteverted or anteflexed, both of which are common.

Image: Shutterstock

  • In the anteverted position, the uterus is bent forward towards the bladder/ pubic bone and towards the front of the body.
  • In anteflexed position, the uterus is rotated towards the pubic bone with a concave surface.

Uncommon uterus positions

Certain positions are tilted back towards the rectum.

  • A retroverted uterus is tipped backward toward the rectum. Around 25% of women have this type of uterus.
  • A retroflexed uterus is the opposite of the anteflexed uterus, as it takes a concave shape towards the rectum (9).

A retro uterus is not known to create any fertility issues. However, you might have pain during sexual intercourse.

A tilted uterus does not usually create a problem during pregnancy, as the changing uterus will retain the forward-tipped position (10).

Research finds
An incarcerated uterus or a trapped uterus is an extremely rare complication of a retroverted uterus (16). A portion of the uterus gets entrapped and expands within the confined areas of the pelvis, which might cause uterine rupture (17).

Measuring The Uterus During Pregnancy

Your doctor might measure the size of your uterus, also called the fundal height (fundus is the domed region at the top of the uterus), to understand the fetal growth and development. The fundal height is the measurement of the top of the pubic bone to the top of the uterus, which determines the gestational age.

Note: It should be noted that the size of the uterus varies from woman to woman and depends on height, weight, and age (11).

You, too, can measure the size of your uterus. Before we go into the various methods of measuring it, let’s see the initial steps:

  1. Lie down on your back on the bed or the floor. While lying down, you should not feel any pain or dizziness.
  1. Locate your uterus by touching your tummy. If you are over 20 weeks pregnant, you can feel the uterus just above the navel. The uterus is hard, round.
  1. Now, move your fingers upward to feel the top of the uterus, which is also referred to as fundus.
  1. Proceed to locate your pubic bone. It is positioned just above your pubic hair line. The bone tip that you can feel is the pubic bone.

Once you locate the fundus and the pubic bone, you can measure the fundal height using various methods.

1. Measuring fundal height using a tape measure

  • Measure the distance between your fundus and the pubic bone in centimeters using a tape.
  • For example, if you are 24 weeks pregnant, then your uterus would usually measure 22-26cm. The uterus usually grows 1cm in a week or about 4cm in a month.

You can use this method to track your pregnancy growth week by week. However, studies say that more research needs to be done to find out the reliability of this method.

2. Measuring the fundal height using the finger method

  • If your uterus is below or above the belly button, then measure how many fingers below or above is the uterus from the bellybutton.
  • The assumption is the fundal height increases by two finger-widths every month.
  • For example, if you are 4 two-finger-widths above the belly button, then it indicates seven months gestation (see the above figure).

This method helps determine the gestational age in months (12).

If you find the fundal height different from the gestational week that you think you are in, talk to your doctor, and get your doubts cleared.

The size of the uterus during pregnancy plays an important role in the well-being of your baby growing inside. Next, we look at how you can maintain the health of your uterus during pregnancy.

How To Keep Your Uterus Healthy?

The best way to keep your uterus healthy is to keep yourself healthy. Here is how you can do it:

  • Make sure to eat right and engage in some forms of exercise to maintain.
  • Quit smoking as it has harmful effects on the uterus.
  • Do not hold your urine.

Frequently Asked Questions

1. When does the mouth of the uterus open in pregnancy?

The opening of the mouth of the uterus is called cervical dilation. The cervix begins to dilate towards the end of pregnancy. It becomes thinner and dilates during the first stage of labor, and is completely dilated by about 10cm during the last stage of labor (13).

2. How does a weak uterus affect pregnancy?

An incompetent or weak cervix, a kind of womb abnormality, may lead to preterm birth in some women (14).

3. Does a swollen uterus mean I am pregnant?

“A swollen uterus could mean pregnancy. Generally speaking, by the time you can appreciate the swelling in your uterus, you will be about three months along. However, there are other reasons for swelling. The most common reason for swelling is fibroids, which are benign smooth muscle tumors,” observes Dr. Lindemann.

The uterus expands during pregnancy, and its growth indicates the size of the fetus. After birth, the uterus again conforms to its previous size. It is beautiful how a small organ grows over time into the size of a watermelon to accommodate a growing fetus. Understanding how your uterus changes throughout pregnancy will help you appreciate the first three trimesters. Because this organ is so important to your health, you must look after it before, during, and after the pregnancy. This entails eating a nutritious diet, exercising regularly, and seeing a gynecologist for regular examinations. Also, notify your gynecologist if you detect any unusual menstrual indications so that the underlying problem can be treated promptly.

Infographic: Interesting Facts About The Uterus

The uterus undergoes several changes throughout a woman’s life, starting from their menstruation cycle, pregnancy, post-pregnancy, and menopause. Therefore, it is no wonder that this organ is a crucial part of their body that holds many intriguing aspects and functions.

So, check this infographic out to learn about the common and not-so-common facts about the uterus.

there is more to your uterus than you know [infographic]
Illustration: MomJunction Design Team


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. The Developing Baby; Parents Centre
2. The First Trimester; John Hopkins Medicine
3. Pregnancy: Starting Out; Women’s Specialists of New Mexico, Ltd
4. Ms. Rajdawinder Kaur1, et al.; A Quasi- Experimental Study to Assess the Effectiveness of Early Ambulation on Involution of Uterus among Postnatal Mothers Admitted At SGRD Hospital, Vallah, Sri Amritsar, Punjab; International Journal of Health Sciences and Research
5. Role of the uterus in fertility, pregnancy, and developmental programming; American Society of Reproductive Medicine
6. Determining the Route and Method of Hysterectomy; Ethicon Endo-Surgery, Inc
7. Wellington de Paula Martins, et al.; Pelvic ultrasonography in children and teenagers; Scielo
8. Anatomy of Female Pelvic Area; John Hopkins Medicine
9. Dr Anne Marie Coady; The uterus and the endometrium Common and unusual pathologies; The British Medical Ultrasound Society
10. Retroverted Uterus; Better Health; Victoria State Government
11. Dr. Ajay M. Parmar, et al.; Sonographic Measurements Of Uterus And Its Correlation With Different Parameters In Parous And Nulliparous Women; International Journal of Medical Science and Education
12. Antenatal Care Module: 10. Estimating Gestational Age from Fundal Height Measurement; The Open University
13. Cervical Ripening; Cleveland Clinic
14. Uterine abnormality – problems with the womb; Tommy’s
15. Cervical insufficiency and short cervix; March of Dimes
16. Incarcerated uterus; Radiopaedia
17. Richard Slama, et al.; (2015)Uterine Incarceration: Rare Cause of Urinary Retention in Healthy Pregnant Patients; National Library of Medicine

Was this article helpful?
The following two tabs change content below.