What is Placenta Previa?

Placenta previa is a life-threatening complication of pregnancy that occurs when the placenta implants in the lower part of the uterus. It occurs in 1 in 200 pregnancies, and is three times more likely to affect women over 30. Although the exact cause of the condition is not always apparent, women who are pregnant with twins or triplets, have an abnormally-shaped uterus, or have scarring in the uterine lining have the highest risk of developing this condition.

Effects

The most common symptom of placenta previa is painless, bright red bleeding from the vagina during the second or third trimester. This bleeding occurs most frequently when the woman is between 27 and 32 weeks pregnant. The amount of blood lost varies. It may be very little or may be enough to require a blood transfusion. Contractions sometimes occur along with the bleeding, putting the woman at risk of delivering the baby prematurely.

Identification

Diagnosis of placenta previa is usually accomplished with ultrasound. Most commonly, a low-lying placenta is noticed during a routine ultrasound performed early in the pregnancy. Although most low-lying placentas do not develop into placenta previa, follow-up scans are performed to track the position of the placenta. If the placenta does not change position as the uterus grows, placenta previa occurs. In some cases, placenta previa is not detected until late pregnancy when the affected woman begins to bleed. Ultrasound is then used to verify the diagnosis.

Types

A low-lying placenta is sometimes a precursor to placenta previa. In this case, although the placenta is located close to the cervix, the pregnancy has not yet progressed to the point where placenta previa can be diagnosed. Marginal placenta previa is when the placenta has implanted close to the cervix but does not block the opening of the cervix. Partial placenta previa refers to a placenta that blocks part of the cervix's opening, while total placenta previa blocks the entire entrance of the cervix and is the most severe form.

Warning

Placenta previa is a dangerous condition and is life-threatening for both the mother and the baby. There is a high risk of severe bleeding during labor, delivery, or soon after delivery. In rare cases, the mother may die from blood loss. Women with placenta previa are also at risk of delivering a premature baby. This can be due to the condition itself triggering pre-term labor, or because an emergency C-section has to be performed early to save the mother's life. Placenta previa occasionally leads to another condition called placenta accreta. This occurs when the placenta implants deeply and cannot be detached from the uterus. Severe bleeding results and a hysterectomy may be required to save the woman's life.

Prevention/Solution

Milder cases of placenta previa are usually treated with bed rest in the patient's own home. This treatment usually allows the pregnancy to continue to term when there is little or no bleeding as a result of placenta previa. The affected woman must stay in bed as much as possible, and cannot exercise, work, or have sex until she has delivered. Brief showers and trips to the bathroom are usually permitted. More severe cases of placenta previa are treated in the hospital with complete bed rest, and in some cases, blood transfusions. Medications are often prescribed to prevent pre-term labor. Patients with placenta previa must deliver their babies via C-section to prevent hemorrhage and severe blood loss.