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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.
normal pregnancy, the placenta is attached higher up in the uterus, away from
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.
pictures of a
normal placenta and placenta previa.
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:
Risk factors that you can't
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.
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:
Call your doctor or go to the nearest emergency room right
away if you have:
Most cases of
placenta previa are found during the second trimester when a woman has a
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.
The kind of treatment you will
have depends on:
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.
Placenta previa can cause problems for both the mother
and the baby. These include:
Learning about placenta previa:
placenta previa include one or both of the
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
ultrasound done for other reasons.
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
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
If you have placenta previa, your treatment will depend
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.
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
Treatment for placenta previa can be done by:
Treatment for a premature infant can be provided by a
If you are pregnant, be alert for any
vaginal bleeding. Sudden, painless vaginal bleeding
may be the only symptom of
placenta previa, a placenta that partially or fully
If you have placenta previa and are not bleeding, it is important to follow certain precautions:
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
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.
American Congress 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.
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 website has information on premature birth, birth
defects, birth defects testing, pregnancy, and prenatal care.
Miller DA (2010). Placenta previa and abruption placentae. In Management of Common Problems in Obstetrics and Gynecology, 5th ed., pp. 57–61. Chichester: Wiley-Blackwell
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
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.
Williams DE, Pridjian G (2011). Obstetrics. In RE Rakel, DP Rakel, eds., Textbook of Family Medicine, 8th ed., pp. 359–401. Philadelphia: Saunders.
February 3, 2012
Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
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