Placenta previa is a complication of pregnancy in which the placenta has implanted in the lower segment of the uterus and is partially or fully blocking the cervix.. It can cause painless bleeding during the second and third trimesters. Learn more about placenta previa and how it can be treated.
Colored pencil drawing of a term fetus with complete placenta previa. The placenta is bleeding.
Image by Bonnie Urquhart Gruenberg
About
An illustration depicting a placenta previa.
Image by BruceBlaus
An illustration depicting a placenta previa.
An illustration depicting a placenta previa.
Image by BruceBlaus
What Is Placenta Previa?
Summary
During pregnancy, the placenta provides the growing baby with oxygen and nutrients from the mother’s bloodstream.
Placenta previa means the placenta has implanted at the bottom of the uterus, over the cervix or close by, which means the baby can’t be born vaginally.
Treatment aims to ease the symptoms and prolong the pregnancy until at least 36 weeks.
During pregnancy, the placenta provides the growing baby with oxygen and nutrients from the mother’s bloodstream. Placenta previa means the placenta has implanted at the bottom of the uterus, covering the cervix.
When a baby is ready to be born, the cervix (neck of the womb) dilates (opens) to allow the baby to move out of the uterus and into the vagina. When a woman has placenta previa (the placenta has implanted at the bottom of the uterus, over the cervix or close by), the baby can’t be born vaginally. ‘Partial placenta previa’ means the cervix is partly blocked, while ‘complete placenta previa’ means the entire cervix is obstructed.
Some of the causes include scarring of the uterine lining (endometrium) and abnormalities of the placenta. Around one in every 200 pregnancies is affected.
An embryo that implants too close to the opening of the cervix can lead to placenta previa, a condition in which the placenta partially or completely covers the cervix.
Image by CNX Openstax
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Embryo with Prominent Yolk Sac, somites, neural tube
Image by TheVisualMD
Embryo with Prominent Yolk Sac, somites, neural tube
Embryo with Prominent Yolk Sac, somites, neural tube
Image by TheVisualMD
What Is Placenta?
The placenta is an organ that supports the diffusion of nutrients and waste between the mother’s and fetus’ blood.
The gestation period is divided into three equal periods or trimesters. During the first two to four weeks of the first trimester, nutrition and waste are handled by the endometrial lining through diffusion. As the trimester progresses, the outer layer of the embryo begins to merge with the endometrium, and the placenta forms. This organ takes over the nutrient and waste requirements of the embryo and fetus, with the parent’s blood passing nutrients to the placenta and removing waste from it. Chemicals from the fetus, such as bilirubin, are processed by the parent’s liver for elimination. Some of the parent’s immunoglobulins will pass through the placenta, providing passive immunity against some potential infections.
Internal organs and body structures begin to develop during the first trimester. By five weeks, limb buds, eyes, the heart, and liver have been basically formed. By eight weeks, the term fetus applies, and the body is essentially formed, as shown in Figure 43.19. The individual is about five centimeters (two inches) in length and many of the organs, such as the lungs and liver, are not yet functioning. Exposure to any toxins is especially dangerous during the first trimester, as all of the body’s organs and structures are going through initial development. Anything that affects that development can have a severe effect on the fetus’ survival.
During the second trimester, the fetus grows to about 30 cm (12 inches), as shown in Figure 43.20. It becomes active and the pregnant person usually feels the first movements. All organs and structures continue to develop. The placenta has taken over the functions of nutrition and waste and the production of estrogen and progesterone from the corpus luteum, which has degenerated. The placenta will continue functioning up through the delivery of the baby.
During the third trimester, the fetus grows to 3 to 4 kg (6 ½ -8 ½ lbs.) and about 50 cm (19-20 inches) long, as illustrated in Figure 43.21. This is the period of the most rapid growth during the pregnancy. Organ development continues to birth (and some systems, such as the nervous system and liver, continue to develop after birth). The pregnant person will be most uncomfortable during this trimester. They may urinate frequently due to pressure on the bladder from the fetus. There may also be intestinal blockage and circulatory problems, especially in the legs, where clots may form due to pressure from the fetus on returning veins as they enter the abdominal cavity.
Contained entirely within the nurturing space of the womb, the developing embryo cannot eat or breathe, and therefore must obtain all nutrients from other sources. For the first nine weeks, the early embryo depends on the yolk sac of the embryo for nourishment. Inside the yolk sac, tiny structures called 'blood islands' form. These will become the first blood and the first blood vessels. As pregnancy continues, these important external structures develop into the embryo's link to the mother's system - the umbilical cord and the supporting network known as the placenta. Until birth, the developing embryo is completely dependent on the mother for nutrients and waste disposal through the umbilical cord and the placenta.
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Meet the Placenta!
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Risk Factors
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
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9 Month Old Twins in-Utero
Interactive by TheVisualMD
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
9 Month Old Twins in-Utero
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9 Month Old Twins in-Utero
Camera is zoomed into face of one fetus. The camera then zooms out to show twins within the womb. The womb is shown positioned above the pelvic girdle. There is no background, only the pelvis gives context of environment. The womb is rendered in the glass-style and the fetuses are semi- translucent. The fetuses are at full term.
Interactive by TheVisualMD
What Are the Causes and Risk Factors of Placenta Previa?
Some of the possible causes and risk factors of placenta previa include:
Low implantation of the fertilised egg
Abnormalities of the uterine lining, such as fibroids
Scarring of the uterine lining (endometrium)
Abnormalities of the placenta
Multiple babies, such as twins
Multiple pregnancies - a woman who has already had six or more deliveries has a risk of one in 20.
What Are the Symptoms of Placenta Previa and Why the Bleeding Happens?
The most important symptom in placenta previa is painless vaginal bleeding after 20 weeks. However, there are causes of vaginal bleeding other than placenta previa. All bleeding during pregnancy should be reported to your doctor for prompt investigation and treatment.
Why the bleeding happens
During the later stages of pregnancy, the bottom part of the uterus thins and spreads to accommodate the growing baby. If the placenta is anchored to the bottom of the uterus (as occurs with placenta previa), this thinning and spreading separates the placenta and causes bleeding.
Sexual intercourse can also cause bleeding from the placenta previa in later pregnancy. During labour, the cervix thins and dilates, which would normally allow the baby to exit into the vagina. In placenta previa, the dilation of the cervix further tears the placenta and causes bleeding.
Withdrawal bleeding (or "fake periods") are different of periods because withdrawal bleeding happens when an hormonal contraception is temporarily stopped while periods are part of the menstrual cycle.
Ultrasound image (sonogram) of a fetus in the womb.
Image by BruceBlaus/Wikimedia
How to Diagnosis Placenta Previa?
A pregnant woman who experiences any vaginal bleeding should be admitted to hospital and tested. Some of the tests used to diagnose placenta previa include:
Ultrasound scan
Feeling the mother’s belly to establish the baby’s position (the baby is sideways or presenting bottom-first in around one in three cases of placenta previa).
Digital vaginal examinations should be strictly avoided
It is sometimes difficult to tell the difference between placenta previa and placental abruption. Placental abruption is a condition where the placenta separates from the uterine wall. Both conditions are flagged by heavy bleeding of bright red blood.
A vaginal examination is often used to help diagnose placental abruption, but could trigger heavier bleeding in the case of placenta previa. An ultrasound scan should always be taken first, and digital (finger) vaginal examinations strictly avoided in the case of placenta previa.
The doctor may do a speculum vaginal examination very gently to make sure the bleeding is not coming from the cervix or vagina. Once the diagnosis is made, the pregnancy needs to be very carefully monitored. Placenta previa is a potentially life-threatening condition for the both the mother and her baby.
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Ultrasound
Ultrasound
Also called: Sonogram
An ultrasound is an imaging test that uses sound waves to create pictures of structures inside the body. It's often used during pregnancy to check the health of an unborn baby. It's also used to diagnose certain medical conditions.
Ultrasound
Also called: Sonogram
An ultrasound is an imaging test that uses sound waves to create pictures of structures inside the body. It's often used during pregnancy to check the health of an unborn baby. It's also used to diagnose certain medical conditions.
An ultrasound is an imaging test that uses sound waves to create a picture (also known as a sonogram) of organs, tissues, and other structures inside the body. Unlike x-rays, ultrasounds don’t use any radiation. An ultrasound can also show parts of the body in motion, such as a heart beating or blood flowing through blood vessels.
There are two main categories of ultrasounds: pregnancy ultrasound and diagnostic ultrasound.
Pregnancy ultrasound is used to look at an unborn baby. The test can provide information about a baby’s growth, development, and overall health.
Diagnostic ultrasound is used to view and provide information about other internal parts of the body. These include the heart, blood vessels, liver, bladder, kidneys, and female reproductive organs.
An ultrasound can be used in different ways, depending on the type of ultrasound and which part of the body is being checked.
A pregnancy ultrasound is done to get information about the health of an unborn baby. It may be used to:
Confirm that you are pregnant.
Check the size and position of the unborn baby.
Check to see you are pregnant with more than one baby.
Estimate how long you have been pregnant. This is known as gestational age.
Check for signs of Down syndrome, which include thickening in the back of the baby's neck.
Check for birth defects in the brain, spinal cord, heart, or other parts of the body.
Check the amount of amniotic fluid. Amniotic fluid is a clear liquid that surrounds an unborn baby during pregnancy. It protects the baby from outside injury and cold. It also helps promote lung development and bone growth.
Diagnostic ultrasound may be used to:
Find out if blood is flowing at a normal rate and level.
See if there is a problem with the structure of your heart.
Look for blockages in the gallbladder.
Check the thyroid gland for cancer or non-cancerous growths.
Check for abnormalities in the abdomen and kidneys.
Help guide a biopsy procedure. A biopsy is a procedure that removes a small sample of tissue for testing.
In women, diagnostic ultrasound may be used to:
Look at a breast lump to see if it might be cancer. (The test may also be used to check for breast cancer in men, though this type of cancer is far more common in women.)
Help find the cause of pelvic pain.
Help find the cause of abnormal menstrual bleeding.
Help diagnose infertility or monitor infertility treatments.
In men, diagnostic ultrasound may be used to help diagnose disorders of the prostate gland.
You may need a ultrasound if you are pregnant. There is no radiation used in the test. It offers a safe way of checking the health of your unborn baby.
You may need diagnostic ultrasound if you have symptoms in certain organs or tissues. These include the heart, kidneys, thyroid, gallbladder, and female reproductive system. You may also need ultrasound if you are getting a biopsy. The ultrasound helps your health care provider get a clear image of the area that is being tested.
A ultrasound usually includes the following steps:
You will lie on a table, exposing the area that’s being viewed.
A health care provider will spread a special gel on the skin over that area.
The provider will move a wand-like device, called a transducer, over the area.
The device sends sound waves into your body. The waves are so high pitched that you can’t hear them.
The waves are recorded and turned into images on a monitor.
You may be able to view the images as they are being made. This often happens during a pregnancy ultrasound, allowing you to look at your unborn baby.
After the test is over, the provider will wipe the gel off your body.
The test takes about 30 to 60 minutes to complete.
In some cases, a pregnancy ultrasound may be done by inserting the transducer into the vagina. This is most often done early in pregnancy.
The preparations will depend on which type of ultrasound you are having. For ultrasounds of the abdominal area, including pregnancy ultrasounds and ultrasounds of the female reproductive system, you may need to fill up your bladder before the test. This involves drinking two to three glasses of water about an hour before the test, and not going to the bathroom. For other ultrasounds, you may need to adjust your diet or to fast (not eat or drink) for several hours before your test. Some types of ultrasounds require no preparation at all.
Your health care provider will let you know if you need to do anything to prepare for your ultrasound.
There are no known risks to having an ultrasound. It is considered safe during pregnancy.
If your pregnancy ultrasound results were normal, it doesn’t guarantee you’ll have a healthy baby. No test can do that. But normal results may mean:
Your baby is growing at a normal rate.
You have the right amount of amniotic fluid.
No birth defects were found, though not all birth defects will show up on an ultrasound.
If your pregnancy ultrasound results were not normal, it may mean:
The baby is not growing at a normal rate.
You have too much or too little amniotic fluid.
The baby is growing outside the uterus. This is called an ectopic pregnancy. A baby can’t survive an ectopic pregnancy, and the condition can be life threatening for the mother.
There is a problem with the baby’s position in the uterus. This could make delivery more difficult.
Your baby has a birth defect.
If your pregnancy ultrasound results were not normal, it doesn’t always mean your baby has a serious health problem. Your provider may suggest more tests to help confirm a diagnosis.
If you had diagnostic ultrasound, the meaning of your results will depend on which part of the body was being looked at.
If you have questions about your results, talk to your health care provider.
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Embryo at Carnegie Stage 23 Inside Womb
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Obstetric ultrasonography
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Twins
Monoamniotic twins at 15 weeks : Abdominal ultrasonography of monoamniotic twins at a gestational age of 15 weeks. A coronal plane is shown of the twin at left, and a sagittal plane of parts of the upper thorax and head is shown of the twin at right.
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Fetal Ultrasound
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Colorized Ultrasound of Possible Breast Tumor
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Sonogram Projected on belly
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Annalisa McCormick, spouse of Airman 1st Class Kristopher McCormick, a 35th Civil Engineer Squadron pavement and equipment journeyman, takes a photo of her baby during an ultra sound appointment at Misawa Air Base, Japan, April 10, 2019. An ultrasound, also called a sonogram, monitors fetal development and screens for any potential medical concerns. (U.S. Air Force photo by Senior Airman Collette Brooks)
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Haggstrom, Mikael. Medical gallery of Mikael Haggstrom 2014
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Obstetric ultrasonography
Staecker
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U.S. Air Force photo by Senior Airman Collette Brooks
Treatment
This picture depicts a laboring mom in the hospital appearing to be experiencing labor pains.
Image by Pixabay - user:Parentingupstream
This picture depicts a laboring mom in the hospital appearing to be experiencing labor pains.
This picture depicts a laboring mom in the hospital appearing to be experiencing labor pains.
Image by Pixabay - user:Parentingupstream
How Placenta Previa Is Treated?
Treatment options vary
Treatment depends on a number of factors, including:
Whether the placenta previa is complete or partial
The exact location of the placenta
The amount of blood lost
The gestational age of the baby
The position of the baby
The health of the baby
The health of the mother.
Treatment during pregnancy
Medical treatment aims to ease the symptoms and prolong the pregnancy. Options may include:
Bed rest.
Hospitalisation.
Close monitoring, such as using a fetal monitor and regularly checking the mother’s vital signs (for example, blood pressure).
Blood transfusion for the mother.
Avoiding any activity that triggers uterine contractions or irritates the cervix, such as sexual intercourse or orgasms.
Delivery
Once the baby is old enough to be delivered, a caesarean section is usually performed. The baby may need to be monitored in intensive care to make sure all is well. The mother will undergo a range of tests, including tests to check her blood cell counts and the clotting ability of her blood.
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Placenta Previa
Placenta previa is a complication of pregnancy in which the placenta has implanted in the lower segment of the uterus and is partially or fully blocking the cervix.. It can cause painless bleeding during the second and third trimesters. Learn more about placenta previa and how it can be treated.