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Uterus During Pregnancy: Its Size, Changes And Role

  • What is the uterus made of?
  • What does the uterus do during pregnancy?
  • What is the size of the uterus?
  • How is the uterus positioned?
  • Trimester-wise changes in the uterus
  • How to measure uterus during pregnancy?
  • How to keep your uterus healthy?

We associate pregnancy with a growing tummy. This one particular change is too visible to ignore, but what we can’t see are numerous changes happening inside. One of the most prominent and crucial changes happens to your uterus as it is the epicenter of your pregnancy.

Your uterus stretches and increases enormously throughout the pregnancy to hold the developing baby. Here, MomJunction explains the changes that happen to your uterus so that you know more about this inconspicuous organ that is the home to your baby for nine months.

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

What Is The Uterus Made Of?

The uterus is an inverted, pear shaped, and a hollow, muscular reproductive organ (1) located in the pelvic region of a woman’s body.

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.

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.

Functions of the uterus during pregnancy

During pregnancy, the uterus:

  • accepts the fertilized ovum that passes through the fallopian tube.
  • creates 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, shrinks back and starts preparing for the next menstrual cycle.The other functions of uterus include:
    • helps the blood flow into the ovaries.
    • supports other organs such as the vagina, bladder, and the rectum.
    • plays an important role in sexual functions like triggering orgasm.

    It helps the blood flow into the ovaries.It supports other organs such as the vagina, bladder, and the rectum.It plays an important role in sexual functions like triggering orgasm.

Normal Size Of A Uterus In Women

The size of uterus varies from woman to woman. It weighs approximately 70 to 125gm (2). However, the size of the uterus is based on the factors like 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 (3).

  • 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 as the size of the uterus is not the same among all the women, the position, too, is not. It can be positioned anteverted, anteflexed, or some other position.

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 utererine position is straight and vertical.

Common uterus positions

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

  • 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 backward towards the rectum.

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

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 forward-tipped position (4).

Physiological Changes In Uterus Through The Pregnancy

As you know, uterus keeps changing in shape and size as your pregnancy progresses. The uterus expansion is between 500 and 1,000 times its normal size (5). Let’s see how the organ changes during each trimester.

Size during the first trimester (0 to 12 weeks):

  • At 12 weeks of pregnancy, the size of uterus remains as small as the size of a grapefruit (6).
  • As your pregnancy progresses, the uterus grows, putting pressure on the bladder. This is the time when your frequency of urination increases (7).
  • In the case of twins or multiple pregnancies, the stretching of the uterus will be faster compared to that in the case of a single baby.

Size during 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 and the breasts and starts putting thrust on the other organs pushing them away from their original positions (8). This may lead to some tensions in 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.

Size during 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.

Size after childbirth:

  • After childbirth, the uterus shrinks back to its normal position. This process is known as involution, which will take about six to eight weeks (9).

Apart from the changes in the size, the uterus undergoes several other anatomical changes.

Measuring The Uterus During Pregnancy

Your doctor will 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.

You, too, can measure the size of your uterus. Before we go into the various methods of measuring the height, let’s see the initial steps (10):

  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 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 safe 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 must 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.

2. Measuring the fundal height using 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 bellybutton, then it indicates 7 months gestation (see the above figure).

This method is helpful in finding the gestational age in terms of months.

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.

Now you know how important the uterus and its size are for the well-being of your baby growing inside. Therefore, let us see how you can maintain the health of your uterus during pregnancy.

How To Keep Your Uterus Healthy?

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.
  • Eat omega-3 fatty acid-rich food.
  • Quit smoking as it has harmful effects on the uterus.
  • Do not hold your urine.

As the pregnancy progresses gradually, you may not know the changes happening inside your body. Whether you can identify the changes or not, you need to take care of your uterus before, during and after pregnancy to avoid any health problems to you or the baby.

Do you have any more information to share? Let us know in the comment box.

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