Placenta Previa

Overview

The placenta is an important organ that develops during pregnancy in order to facilitate and support the growth of the fetus in the uterus. It connects the fetus to the wall of the uterus by means of the umbilical cord. The role of the placenta is to provide the developing fetus with oxygen and nutrients and to clear away wastes from the fetal blood. When fetal development is complete and the baby is ready to be born, its head must pass through the dilated cervix and into the birth canal. After childbirth, the placenta no longer has any use and is then expelled from the body in the form of afterbirth. Placenta previa is a pregnancy complication that affects 1 in every 200 pregnant women.

What Is Placenta Previa?

Usually, the placenta is located well away from the cervix so that the fetus can pass through the cervical canal into the vagina. Sometimes, though, the placenta may be located low along the uterine wall. It can end up partially or completely obscuring the opening of the cervix. This is known as placenta previa.

It is a kind of obstetric complication. It is, in fact, fairly common for the placenta to be situated low in the uterus during the early part of pregnancy. As the pregnancy progresses, however, the placenta may move further up into the uterus, clearing the way for delivery. In instances where the placenta remains close to the cervix, there is a danger of bleeding and further pregnancy complications.

What Are Some Risk Factors Associated With Placenta Previa?

It is believed that any condition that causes damage to the uterus can potentially increase the risk of developing placenta previa. This includes surgery on the uterus or procedures such as dilation and curettage for abortion. Past Caesarean section can also increase the risk of developing a low-lying placenta in the next pregnancy.

The exact cause of placenta previa is not well understood. However, research has enabled identification of certain factors that are associated with an increased likelihood of placenta previa, such as those mentioned above. These are known as risk factors. Having one of the following risk factors does not mean that you will necessarily develop placenta previa, but that it will be more likely.

• Smoking during pregnancy.
• Taking cocaine during pregnancy.
• A particularly large placenta.
• In-vitro fertilization.
• Being younger than 20 years of age or older than 35 at the time of pregnancy.
• Being pregnant with multiple fetuses.
• The risk is higher in women who have had several pregnancies in the past.
• Having an abnormally shaped uterus.
• Having a history of placenta previa.
• Women who have previously undergone a Caesarean section are twice as likely to suffer from placenta previa as compared to others.
• Having a fetus in an abnormal position such as the breech position.
• Previous surgery for removal of fibroids.
• Damage to the endometrium or the inner lining of the uterus.

What Are The Identifying Signs Of Placenta Previa?

The classic identifying symptom of placenta previa is painless vaginal bleeding. During labor, the cervix begins to dilate in preparation for childbirth. As it does so, it can cause a rupture in the blood vessels linking the placenta and the uterus if the placenta is located too close to the cervix or actually obscuring it. This is what is responsible for the bright red vaginal bleeding.

Other than bleeding during the latter part of the pregnancy, a woman with placenta previa may not actually know about her condition unless it is noticed during the ultrasound. Bleeding begins suddenly, often during the second or third trimesters. Some women may even have contractions or cramps along with the bleeding. The extent of bleeding varies from one individual to the next.

What Are The Different Types Of Placenta Previa?

According to the extent of the condition, placenta previa can be graded as either marginal, partial or complete. A marginal case of placenta previa is one in which the placenta is located at the edge of the cervix but isn’t actually obstructing it. A partial case of placenta previa, as the name indicates, involves partial obstruction of the cervix by the placenta. Complete placenta previa involves the placenta completely covering the cervix.

What Are Some Probable Complications?

A pregnancy complicated by placenta previa will most likely require a Caesarean section for delivery. Normal vaginal birth would be too risky since it could cause excessive bleeding to the extent that it could endanger the lives of both mother and child. A more detailed list of potential complications appears below:

• Severe bleeding.
• Spontaneous abortion.
• Fetal malpresentation.
• Postpartum hemorrhage.
• Risk of postpartum infections.
• Higher likelihood of delivery by means of Caesarean section because placenta previa makes it difficult to achieve proper contractions.
• Premature delivery in approximately 50% of cases. The baby may even be born before certain organs have developed properly.
• Risk of fetal death increases by 3 to 4 times.

What Tests Are Needed To Diagnose Placenta Previa?

The doctor may suspect placenta previa based on indications such as the bleeding and the premature contractions. Tests generally include:

• Ultrasound imaging.
• Magnetic resonance imaging (MRI).

Once it has been confirmed that the placenta is positioned too close to the cervix or actually obstructing it, the mother will typically be asked to take bed rest. She will be asked to refrain from any kind of physical exertion. In case of severe blood loss, she may be given blood transfusions. If the doctors feel that vaginal birth is not feasible, the baby will be delivered by Caesarean section. The treatment mainly aims to manage the bleeding caused as a result of placenta previa. There are no surgical or medical treatment modalities devised in order to cure placenta previa.

The treatment modality opted is chiefly based on the factors such as the relative position of the placenta and the fetus,  length of the pregnancy, the amount of bleeding, the overall health of the female and the fetus and many more. The treatment also aims to get close to the due date of pregnancy as much as possible in case the placenta previa does not resolve. In general, all females with placenta previa have to undergo a cesarean delivery.

Doctors advise that activities that can trigger bleeding (such as exercise and sex) should be avoided. Ideally, after 36 weeks of pregnancy, a C-section can be planned with the goal of delivering the baby safely. However, in case of persistent heavy bleeding or multiple bleeding episodes, the delivery might be planned earlier.

If the baby is delivered before 37 weeks of pregnancy, corticosteroids are prescribed to the female in order to facilitate the development of the lungs of the baby. An emergency C-section is planned even if the fetus is premature in cases where the fetus is in distress or the bleeding is uncontrollable. There are no methods devised to prevent placenta previa. However, taking care of the risk factors (smoking, maternal age, multiple pregnancies etc.) is a feasible option.

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