Placenta previa (pluh-SEN-tuh PREH-vee-uh) is a problem during pregnancy when the placenta completely or partially covers the opening of the uterus (cervix).
The placenta is an organ that develops inside the uterus during pregnancy. It works to provide oxygen and nutrition to the baby and to remove waste. The placenta connects to your baby through the umbilical cord. Typically, the placenta is attached to the top or side of the inner wall of the uterus.
With placenta previa, the placenta attaches lower in the uterus. This results in some portion of the placental tissue covering the cervix. It can result in bleeding during the pregnancy or during or after delivery.
Changes in the uterus and placenta during pregnancy may lead to the problem correcting on its own. If it doesn't, the baby is delivered by cesarean section (C-section).
The main sign of placenta previa is bright red vaginal bleeding, usually without pain, after 20 weeks of pregnancy. Sometimes, spotting happens before an event with more blood loss.
The bleeding may occur with prelabor contractions of the uterus that cause pain. The bleeding may also be triggered by sex or during a medical exam. For some women, bleeding may not occur until labor. Often there is no clear event that leads to bleeding.
If you have vaginal bleeding during your second or third trimester, call your health care provider right away. If the bleeding is severe, seek emergency medical care.
The exact cause of placenta previa is unknown.
Placenta previa is more common among women who:
If you have placenta previa, your health care provider will monitor you and your baby to reduce the risk of these serious complications:
Placenta previa is diagnosed through ultrasound, either during a routine prenatal appointment or after an episode of vaginal bleeding. Most cases of placenta previa are diagnosed during a second-trimester ultrasound exam.
The initial diagnosis may be done with an ultrasound device on your abdomen. For more accurate images, you may also need a transvaginal ultrasound, which uses a wandlike device placed inside your vagina. Your provider will take care with the position of the device so as not to disrupt the placenta or cause bleeding.
If placenta previa is diagnosed during a routine exam, you'll likely have more-frequent ultrasound exams to monitor any changes in the placenta.
In many women diagnosed with placenta previa early in their pregnancies, the condition resolves on its own. As the uterus grows, the distance between the cervix and the placenta may increase. Also, the direction of growth of the placenta may be higher in the uterus, and the edges of placental tissue near the cervix may shrink.
If placenta previa resolves, you may be able to plan for a vaginal delivery. If it doesn't resolve, you'll plan for a C-section delivery.
Vaginal bleeding after 20 weeks is treated as a medical emergency. You may be admitted to the hospital's labor and delivery unit. You and your baby will be monitored, and you may need a blood transfusion to replace lost blood.
If you are at 36 weeks, you'll likely have a C-section to deliver the baby. If you have extreme blood loss or there's a risk to the health of you or the baby, an emergency C-section may be needed before 36 weeks.
If this was the first time you've had bleeding and the bleeding has stopped for at least 48 hours, you may be sent home from the hospital. If you continue to have episodes of heavier bleeding, your health care team may recommend that you remain in the hospital.
When there's no bleeding, the treatment goal is to lower the risk of possible bleeding and to get you as close to your delivery date as possible. Your care provider will likely recommend you avoid the following:
If you are sent home from the hospital after a first bleeding episode, you'll be expected to follow these same recommendations to lower the risk of a second episode.
You'll be advised to get emergency medical care if you have vaginal bleeding or contractions. Your health care provider may ask whether you have support at home that allows for transportation to a nearby hospital.
Even if you've had no bleeding during your pregnancy due to placenta previa — or no bleeding since the first episode — you'll likely have a C-section delivery scheduled sometime between 36 and 37 weeks.
If your delivery is planned before 37 weeks, your health care provider will offer you corticosteroids to help your baby's lungs develop.
If you're diagnosed with placenta previa, you may worry about how your condition will affect you, your baby and your family. Some of these strategies might help you cope:
Placenta previa is usually diagnosed during a routine ultrasound exam or after an episode of vaginal bleeding. So you might not have time to prepare for an appointment about placenta previa as you might for typical prenatal care appointments.
If you don't need immediate medical care or are being sent home after treatment for vaginal bleeding, it's important to understand the plan for ongoing care and management.
Questions you may want to ask your provider after a diagnosis or at follow-up exams include:
Your health care provider is likely to ask you a number of questions, regarding your ability to manage care at home, particularly if you've already had one bleeding episode. These include:
