Definition

Placenta previa is a pregnancy condition where the placenta is positioned at the lower part of the uterus, covering part or all of the cervix (the neck of the womb). The placenta is an organ that develops in the uterus during pregnancy, providing oxygen and nutrients to the baby while removing waste products. The placenta connects the mother and fetus through the umbilical cord. Typically, the placenta attaches to the upper or side walls of the uterus.

In placenta previa, the placenta is attached to the lower part of the uterus, which can partially or fully cover the cervix. This condition can lead to bleeding during pregnancy or delivery. It occurs in about 1 in 200 pregnancies.

Causes

During pregnancy, the placenta grows as the uterus enlarges. In early pregnancy, it is normal for the placenta to be attached to the lower part of the uterus. As the pregnancy progresses, the placenta usually moves towards the top of the uterus. By the third trimester, the placenta should be near the top of the uterus. This allows the cervix to open, enabling the baby to pass through the birth canal.

Therefore, if the placenta covers part or all of the cervix, the baby cannot come out of the uterus. The exact cause of placenta previa in pregnant women is still unknown.

There are several types of placenta previa based on the location of the placenta in the uterus:

• Marginal placenta previa: The placenta is next to the cervix but does not cover the uterine opening. This type of placenta previa is the most likely to resolve on its own before the due date.
• Partial placenta previa: The placenta partially covers the uterine opening.
• Complete placenta previa: The placenta covers the entire uterine opening. This type of placenta previa is less likely to move upwards on its own.

All types of placenta previa can cause vaginal bleeding during pregnancy and delivery.

Additionally, we have an article about postpartum hemorrhage that you can read here: Compensation Of Childbirth - Definition, Cause And Risk Factors

Risk Factor

Placenta previa is more common in women who:

• Have had multiple pregnancies
• Are aged 35 or older
• Are carrying twins or more
• Have scars on the uterus from previous miscarriages, procedures, or surgeries (such as dilation and curettage, cesarean sections, etc.)
• Have a uterine abnormality
• Have had placenta previa in a previous pregnancy
• Became pregnant through in vitro fertilization
• Smoke or use cocaine

Symptoms

The main symptom of placenta previa is bright red vaginal bleeding occurring after the 20th week of pregnancy, typically near the end of the second trimester or early third trimester. The bleeding may begin with spotting beforehand.

Bleeding may occur due to sexual activity or during medical examinations. In some women, bleeding may not happen until labor begins. Often, bleeding occurs spontaneously without any preceding activity.

Placenta previa is an emergency because the bleeding can be severe and life-threatening for the mother. The bleeding may stop on its own but can reoccur days or weeks later. Sometimes, bleeding does not occur until labor begins.

Some women may also experience cramping or pain in the abdomen or back.

Diagnosis

Placenta previa is diagnosed through ultrasound (USG), either during a routine pregnancy check-up or after experiencing vaginal bleeding. Most cases of placenta previa are detected during a second-trimester ultrasound.

An initial diagnosis can be made with an abdominal ultrasound. For a more accurate image, a transvaginal ultrasound may be needed to confirm the location of the placenta, where the ultrasound probe is inserted into the vagina. The doctor will be careful when using the probe to avoid disturbing the placenta or causing bleeding.

Management

If placenta previa is diagnosed during a routine check-up, you will be advised to undergo regular ultrasounds to monitor any changes in the placenta's location.

In many women with placenta previa in the second trimester, the condition may improve on its own. As the uterus grows, the distance between the cervix and placenta may increase. Additionally, the placenta may grow higher up in the uterus, and the part of the placenta near the cervix may shrink.

If placenta previa improves, you can plan for a normal delivery. However, if the placenta's location does not change, a cesarean delivery will be recommended, especially if the pregnancy has reached 36 weeks. A cesarean is the safest method, particularly if you experience bleeding. In cases where delivery is planned before 37 weeks, the doctor may give medication to help the baby's lungs mature.

Vaginal bleeding after 20 weeks of pregnancy will be treated as an emergency. Both you and your baby will be monitored, and a blood transfusion may be given if the bleeding is excessive. If there is no bleeding but placenta previa is detected, you may be advised to reduce your activity level and avoid the following:

• Excessive sexual activity
• Using tampons or douching
• Moderate to heavy exercise, such as weightlifting
• Prolonged standing

Complications

If you have placenta previa, the doctor will monitor you and your baby to minimize the risk of serious complications such as:

• Heavy vaginal bleeding that can be life-threatening and may occur during pregnancy, delivery, or several hours after delivery.
• Severe bleeding that may require an emergency cesarean, even before the baby is full-term, when essential organs like the lungs are not fully developed.
• The placenta attaches deeply into the uterus, increasing the risk of bleeding during pregnancy and delivery.

Prevention

There is no way to prevent placenta previa. You can identify your risk factors and consult your doctor during pregnancy check-ups to plan your delivery. Avoid smoking and using cocaine, as they can increase the risk of this condition.

When to See a Doctor?

If you experience vaginal bleeding during the second or third trimester, immediately contact the doctor. Heavy bleeding requires immediate treatment to save you and your fetus. The previa placenta can be harmful to you and your fetus.

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