Placenta Previa

What is Placenta Previa?

Placenta Previa is a condition that is considered to be a pregnancy complication. The placenta is the fluid and nutrient filled sac that surrounds the fetus as it grows and develops. When a pregnant woman develops placenta previa, it means that the placenta has grown in such a way that it covers the opening of the cervix. The placenta may cover all or just a part of the cervix.

In a “normal” pregnancy, the placenta attaches itself higher in the uterus so that it will not block the opening of the cervix. Placenta previa involves an abnormally low placenta later in a woman’s pregnancy. It is quite normal during early pregnancy for the placenta to be lower in the uterus, but as the pregnancy progresses, the placenta generally moves up in uterus leaving the cervix and the birth canal unobstructed.

There are many potential causes for placenta previa. If a woman has a uterus that is not normally shaped (either due to genetics or from scar tissue from previous cesarean deliveries or uterine surgeries), they may be more likely to suffer placenta previa. A woman who has had numerous other children, is pregnant with more than one child, or is pregnant through the assistance of in vitro fertilization may also be more prone to placenta previa.

What are the Symptoms of Placenta Previa?

Sometimes, placenta previa causes no symptoms at all. However, the most common symptoms of the condition are cramping and vaginal bleeding. This vaginal bleeding may be severe and usually occurs at the end of the second trimester or beginning of the third. The bleeding may stop on its own and return at a later time or may be continuous. Vaginal bleeding to placenta previa may be life-threatening.

Placenta Previa Causes

Placenta previa occurs when the fertilized egg implants too low in the uterus, and the placenta forms near or over the cervix. Abnormalities in the endometrium (uterine lining) due to fibroids, incisions, C-sections or abortions can also cause recurring previa.

Sometimes, it’s a simple matter of the placenta forming atypically. If you are pregnant with multiples, you are twice as likely to develop placenta previa. In some cases, where the mother has been pregnant six times or more, the chances of having a placenta previa pregnancy increase to 1 in 20.

Scientists don’t know the exact cause for the placenta to form near or over the cervical opening in the uterus. Other possible causes include a caesarean section delivery or other surgery on the uterus. Scar tissue inside the uterus can also be a contributing factor.

If the mother smokes or uses cocaine that can increase the risk of developing the condition. If the mother is 30 or older, the risk of placenta previa developing triples when compared to a 20 year old woman. Another possible cause is a pregnancy that was conceived with the help of in-vitro fertilization or other assisted reproduction.

How is Placenta Previa Treated?

Because a placenta previa blocks the birth canal, there is a high risk of heavy bleeding during delivery that could be life-threatening to mother and child both. As such, a cesarean delivery is often necessary. If the condition is detected via ultrasound before labor begins, a doctor may recommend a scheduled cesarean after 36 weeks of pregnancy. Also, when a placenta previa is detected early, bed rest and reduced activities, and even hospitalization or medications and blood transfusions may be necessary.

Placenta Previa Prevention

Doctors don’t yet know how to prevent placenta previa. In order to reduce your chances of developing this condition, refrain from smoking or using cocaine prior to conception and during your pregnancy.

Another way to prevent placenta previa in future pregnancies is to avoid having a C-section, unless it is absolutely a medical requirement. If you are experiencing a low-risk pregnancy with no compelling reason to have a caesarian, the best course of action is most likely to let labor occur naturally. Each C-section increases your risk of placenta previa.

A more extreme measure, if you had already had one or more pregnancies with placenta previa, is to forgo future pregnancies that can endanger the health of mother and child.

Last Reviewed:
October 08, 2016
Last Updated:
January 02, 2018