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What Is Placenta Previa?
With placenta previa, the placenta lies close to the cervix or covers the cervix. Placenta previa is serious because of the chance of heavy bleeding. Bleeding may occur during pregnancy or during labor.
This problem is not common; it happens about once in every 170 pregnancies.
The cause of placenta previa is not completely understood. Risk factors for an increased chance of placenta previa include previous Cesarean delivery, many pregnancies and increased maternal age.

Symptoms of Placenta Previa

The most characteristic symptom of placenta previa is painless bleeding without any contractions of the uterus. This doesn't usually occur until close to the end of your second trimester or later when the cervix thins out, stretches and tears the placenta loose.

Bleeding with placenta previa may occur without warning and may be extremely heavy. It occurs when the cervix begins to dilate with early labor, and blood escapes.

Placenta previa should be suspected when a woman experiences vaginal bleeding during the latter half of pregnancy. The problem cannot be diagnosed with a physical exam because a pelvic examination may cause heavier bleeding. Doctors use ultrasound to identify placenta previa. Ultrasound is particularly accurate in the second half of pregnancy as the uterus and placenta get bigger.

If you know you have placenta previa, your healthcare provider may tell you not to have a pelvic exam. This is important to remember if you see another caregiver or when you go to the hospital.
The baby is more likely to be in a breech position with placenta previa. For this reason, and to control bleeding, a Cesarean delivery is usually performed. Cesarean delivery with placenta previa offers the healthcare provider the advantage of delivering the baby, then removing the placenta so the uterus can contract. Bleeding can be kept to a minimum.

The placenta is an organ that forms on the inner wall of the uterus shortly after conception. Placenta previa is diagnosed with ultrasound. As the lower uterus grows, the position of the placenta can change in relation to the cervix so that by the end of the pregnancy, the placenta no longer blocks the cervix.