What is placenta previa?
Placenta previa is a problem with the placenta during pregnancy. The placenta is a round, flat organ that forms during pregnancy to give the baby food and oxygen from the mother. The placenta forms on the inside wall of the uterus soon after conception.
During a normal pregnancy, the placenta is attached higher up in the uterus, away from the cervix. But in rare cases, the placenta forms low in the uterus. If this happens, it may cover all or part of the cervix. When the placenta blocks the cervix, it is called placenta previa.
See pictures of a normal placenta and placenta previa.
What causes placenta previa, and how can you lower your risk?
Doctors aren't sure what causes placenta previa. But there are things that raise a woman’s risk of it. These things are called risk factors. Some risk factors you can control to lower your risk. Others are things you can't control.
Risk factors for placenta previa that you can control include:
- Smoking during pregnancy.
- Using cocaine during pregnancy.
Risk factors that you can't control include:
- Past surgeries or tests that affected the lining of the uterus, such as uterine surgery, dilation and curettage (D&C), or myomectomy.
- Past cesarean delivery (C-section) .
- A history of five or more past pregnancies.
- Being 35 or older.
- A history of a past placenta previa.
If your doctor finds out before your 20th week of pregnancy that you have a placenta that is attached low in the uterus, chances are good that it will get better on its own. In fact, 9 out of 10 cases found before the 20th week go away on their own by the end of the pregnancy.1 This is because as the lower uterus grows, the position of the placenta can change. So by the end of the pregnancy, the placenta may no longer block the cervix.
What are the symptoms?
Some women with placenta previa do not have any symptoms. But there are a few warning signs. If you have placenta previa, you may notice one or more symptoms. These include:
- Sudden, painless vaginal bleeding that is light to heavy. The blood is often bright red.
- Symptoms of early labor, such as regular contractions and aches or pains in your lower back or belly.
Call your doctor or go to the nearest emergency room right away if you have:
- Medium to severe vaginal bleeding during the first trimester.
- Any vaginal bleeding in the second or third trimesters.
How is placenta previa diagnosed?
Most cases of placenta previa are found during the second trimester when a woman has a routine ultrasound. Or it may be found when a pregnant woman has vaginal bleeding and gets an ultrasound to find out what is causing it. Some women find out that they have placenta previa only when they have bleeding at the start of labor.
How is it treated?
The kind of treatment you will have depends on:
- How much you are bleeding.
- How the problem is affecting your health and your baby’s health.
- How close you are to your due date.
If you have placenta previa and aren't bleeding, it is important to avoid having sex or vaginal exams and to avoid putting anything else in your vagina. (But you may have a carefully done vaginal exam at the hospital.) You should see your doctor if you have any bleeding.
If you are bleeding, you may have to stay in the hospital. When your baby is mature enough, or if too much bleeding is putting you or your baby in danger, your baby will be delivered. Doctors always do a cesarean section when there is a placenta previa. This is because the placenta can be disturbed with a vaginal delivery, and it can cause severe bleeding.
What are the possible problems from having placenta previa?
Placenta previa can cause problems for both the mother and the baby. These include:
- A condition called placenta abruptio. This means that the placenta breaks away from the wall of the uterus before the baby has been born.
- Severe bleeding in the mother before or during delivery. This can be very dangerous for both the mother and the baby. If the placenta has attached or grown into the wall of the uterus (known as placenta accreta, placenta increta, or placenta percreta), the bleeding can be heavy enough to require a hysterectomy.2
- Having to deliver the baby too early.
- Birth defects. These occur more often in pregnancies with placenta previa than in pregnancies without this problem.
Frequently Asked Questions
Learning about placenta previa:
Symptoms of placenta previa include one or both of the following:
- Sudden, painless vaginal bleeding that ranges from slight to heavy. The blood is often bright red. Bleeding can occur as early as the 20th week of pregnancy but is most common during the third trimester.
- Symptoms of preterm labor, such as regular, menstrual-like cramps, or a feeling of pressure in your lower abdomen. The bleeding from placenta previa can cause the uterus to contract.
Bleeding from placenta previa may taper off and even stop for a while. But it nearly always starts again days or weeks later.
Some women with placenta previa do not have any symptoms. In this case, placenta previa may only be diagnosed by an ultrasound done for other reasons.
Exams and Tests
An ultrasound test is used to diagnose a low-lying placenta or placenta previa, in which the placenta partially or fully covers the cervix. But ultrasound does not always provide a clear picture of the placenta's location.
Unless an immediate cesarean delivery is planned, a pelvic (vaginal) examination is not done because of the risk of further injuring the placenta, causing heavier bleeding.
Electronic fetal heart monitoring is used to check the fetus's condition.
When an early delivery is needed, an amniocentesis may be done. It is used to find out whether the fetus's lungs are ready to breathe well after birth. For an amniocentesis, a needle is inserted into the mother's belly to take a small sample of amniotic fluid from inside the uterus. This fluid is made by the fetus's lungs. A lab test of the fluid can test for signs that the lungs are well developed.
If you have placenta previa, your treatment will depend upon:
- How much you are bleeding (which influences whether you are monitored as an outpatient or in the hospital), whether you need a blood transfusion, and when delivery is necessary.
- Your overall physical condition, such as whether you've lost blood and are anemic.
- Your fetus's overall maturity and physical condition. Whenever possible, delivery is delayed until fetal lungs are mature.
- How much of your cervix is covered by the placenta. Because a vaginal delivery is likely to cause heavy placental bleeding, a cesarean is used for placenta previa deliveries.
If you have placenta previa and are not bleeding, it is important to follow certain precautions:
- Avoid all strenuous activities, such as running or lifting more than approximately 20 lb (9.1 kg).
- See a doctor immediately if you have any bleeding. Be sure that he or she knows you have placenta previa.
- Have a phone nearby at all times.
- Advise all health professionals who examine you that you must not have pelvic exams.
- Refrain from sexual intercourse after 28 weeks of pregnancy. Before 28 weeks, ask your health professional about any possible risks.
- Avoid inserting anything, such as tampons or vaginal douches, into the vagina.
- Be close to a hospital that can provide emergency care for both you and a sick or premature infant.
If you have placenta previa and begin to bleed, you may be hospitalized. If your fetus is mature, you will have a cesarean delivery. If your bleeding slows down or stops, delivery can most likely be delayed. This watching and waiting approach is called expectant management. The course of expectant management is based on your and your fetus's condition.
- If your fetus is 24 to 34 weeks' gestation, you may be given corticosteroids to improve fetal lung development and prepare for an early birth. You may have an amniocentesis to see how developed your fetus's lungs are. You may also be given iron supplements to treat or prevent anemia and a high-fiber diet with stool softeners to ease any straining during a bowel movement. If you have Rh-negative blood, you will be given Rh immunoglobulin in case your fetus has Rh-positive blood. Should you be exposed to your fetus's Rh-positive blood without Rh immunoglobulin, your immune system will develop antibodies that are dangerous to an Rh-positive fetus (Rh sensitization). For more information, see the topic Rh Sensitization During Pregnancy.
- If your bleeding does not stop, expect to remain hospitalized and closely monitored until your fetus is mature enough to deliver. Moderate blood loss can be replaced with a blood transfusion to prolong your pregnancy until your fetus is mature enough to deliver.3
- If you have labor contractions, you may be given tocolytic medicine to slow or stop the contractions. But the benefit of tocolytic medicine in stopping labor is uncertain. For more information, see the topic Preterm Labor.
- Should bleeding become severe and uncontrollable, an immediate cesarean delivery, possibly with a blood transfusion, is the only treatment available for stopping it.
Delivery involving placenta previa is done by cesarean section.
About 25 out of 100 women with placenta previa deliver their babies preterm (before the 37th week of pregnancy).3 Infant problems following placenta previa are usually related to prematurity. If your infant is premature, he or she may need care in a neonatal intensive care unit, or NICU. Care in the NICU can last days or weeks, depending on the extent of a baby's problems and the amount of care needed. For more information, see the topic Premature Infant.
Treatment for placenta previa can be done by:
Treatment for a premature infant can be provided by a neonatologist.
Call 911 or other emergency services right away if you have severe vaginal bleeding. Severe vaginal bleeding means you are passing blood clots and soaking through your usual pad each hour for 2 or more hours (you should not be using tampons).
Call your doctor now or go to the closest emergency room right away if you have any vaginal bleeding.
If you have had placenta previa
After you have had placenta previa, you may have questions about a future pregnancy. Based on the nature of your condition, your doctor will be able to answer your questions and address your concerns.
In very rare cases, placenta previa causes a stillbirth or newborn death. Should you experience such a loss, allow yourself time to grieve. Expect that your partner, children, and other family members may also be deeply affected. Consider meeting with a support group, reading about the experiences of other women, and talking to friends, a counselor, or a member of the clergy to help you and your family cope with your loss. For more information, see the topic Grief and Grieving.
Other Places To Get Help
|American College of Obstetricians and Gynecologists (ACOG)|
|409 12th Street SW|
|P.O. Box 96920|
|Washington, DC 20090-6920|
American College of Obstetricians and Gynecologists (ACOG) is a nonprofit organization of professionals who provide health care for women, including teens. The ACOG Resource Center publishes manuals and patient education materials. The Web publications section of the site has patient education pamphlets on many women's health topics, including reproductive health, breast-feeding, violence, and quitting smoking.
|March of Dimes|
|1275 Mamaroneck Avenue|
|White Plains, NY 10605|
The March of Dimes tries to improve the health of babies by preventing birth defects, premature birth, and early death. March of Dimes supports research, community services, education, and advocacy to save babies' lives. The organization's Web site has information on premature birth, birth defects, birth defects testing, pregnancy, and prenatal care. You can sign up to get a free newsletter and also explore Understanding Your Newborn: An Interactive Program for New Parents.
- Oyelese Y, Smulian JC (2006). Placenta previa, placenta accreta, and vasa previa. Obstetrics and Gynecology, 107(4): 927–941.
- Kay HH (2008). Placenta previa and abruption. In RS Gibbs et al., eds., Danforth's Obstetrics and Gynecology, 10th ed., pp. 387–399. Philadelphia: Lippincott Williams and Wilkins.
- Scearce J, Uzelac PS (2007). Third-trimester vaginal bleeding. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., pp. 328–341. New York: McGraw-Hill.
Other Works Consulted
- Hull AD, Resnik R (2009). Placenta previa section of Placenta previa, placenta accreta, abruptio placentae, and vasa previa. In RK Creasy, et al., eds., Creasy and Resnik's Maternal Fetal Medicine, 6th ed., pp. 731–734. Philadelphia: Saunders Elsevier.
|Author||Sandy Jocoy, RN|
|Editor||Kathleen M. Ariss, MS|
|Associate Editor||Pat Truman, MATC|
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Specialist Medical Reviewer||William Gilbert, MD - Perinatology|
|Last Updated||February 23, 2010|
Last Updated: February 23, 2010