- 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.
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.
[ Read: Uterine Rupture During Pregnancy ]
In addition to holding the baby, uterus also has other roles:
- 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.
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.
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 it can take some abnormal position.
[ Read: Uterine Prolapse During Pregnancy ]
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 considered abnormal, as they 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).
Trimester-wise Uterus Changes During 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.
[ Read: Uterine Abnormalities During Pregnancy ]
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.
Other Changes In The Uterus During Pregnancy
Let’s see what other changes you can expect in the uterus during pregnancy:
- Corpus Luteum is a temporary structure that develops during ovulation. When the egg is not fertilized, it degenerates. But when the egg is fertilized, it continues to be there to support your pregnancy.
- It initiates the secretion of progesterone, which is an important hormone during pregnancy and forms a protective layer surrounding the embryo.
- It also helps in developing the linings around the uterine walls.
- Placenta develops inside the uterus to nurture and support the fetus throughout the pregnancy.
- The placenta is responsible for the secretion of reproductive hormones progesterone and estrogen.
- As the pregnancy proceeds, the blood vessels present in the lining of the uterus will grow bigger and make the uterine line thicker.
- These blood vessels play an important role in nurturing and supporting the growing fetus.
- By the time you are in the third week of pregnancy, the cervix changes in color and texture.
- It develops the mucous plug that stays until your delivery.
- The mucous helps in holding the uterus in position and prevents it from any external contamination.
[ Read: What Is Bicornuate Uterus ]
- It plays an important part in the fetus development during pregnancy.
- Amniotic fluid is a clear liquid that protects the baby inside the uterus from any pressures or thrusts felt on the mother’s stomach.
- It also facilitates the fetus’ movement, which can be felt by the expecting moms.
- The amniotic fluid flows out of the uterus during childbirth.
Change in the lower segment
- As your pregnancy proceeds, the baby grows and stretches the uterus outside the pelvic area.
- By the 12th week, you can feel the uterus by touching your tummy.
- During the 30th week of pregnancy, the myometrium muscles will start stretching and turn the upper part of your uterus thicker. The thinner layers that are left behind are called the lower segment (10).
- The lower segment of the uterus has weaker muscles compared to the upper part. This region gets lower blood supply than the upper part. Therefore, during a Cesarean delivery, the surgery is performed on the lower segment of the uterus.
- Due to lower blood flow in the lower segment, the cut is made above the pubic hair line during C-section to prevent excessive blood loss.
As the pregnancy progresses, the uterus tends to tilt towards the right side. At this stage, the ligaments provide support to the uterus. As the ligaments stretch with the growing pregnancy, it leads to sharp pain in the groin.
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: (11)
- Lie down on your back on the bed or the floor. While lying down you should not feel any pain or dizziness.
- 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.
- Now, move your fingers upward to feel the top of the uterus, which is also referred as fundus.
- 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.
[ Read: Uterine Fibroids During Pregnancy ]
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.
How To Keep Your Uterus 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. These fatty acids help reduce the secretion of a hormone-like substance called prostaglandin, which causes the uterus to contract hard causing pain.
- Quit smoking as it has harmful effects on the uterus.
- Do not hold your urine. Holding urine for long accumulates waste in the bladder, leading to urinary tract infections, which can further spread into the uterus.
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.
[ Read: Cervical Length During Pregnancy ]
Do you have any more information to share? Let us know in the comment box.
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