How Placenta Previa Can Affect Your Pregnancy and Delivery

Pregnancy is a time of change. For many people, that brings a sense of excitement but also worry, especially if there are unexpected bumps in the road. Finding out that you have a placenta previa probably wasn’t something you expected, and you surely have questions about how this can affect your pregnancy. 

Having placenta previa puts you in a “high-risk” pregnancy category. But that doesn’t automatically mean you should expect the worst. In fact, most pregnancies with placenta previa end with safe deliveries. But there are precautions you should take during pregnancy to keep yourself and your baby safe. 

What is placenta previa?

Placenta previa is a condition where the placenta covers part or all of the opening of the cervix. 

The placenta is an important organ that forms during the first trimester. The placenta is the connection between you and your growing fetus. It attaches on one end to your uterus and on the other end to the umbilical cord. It supplies a fetus with oxygen and nutrients and removes its waste.

Usually, the placenta attaches to the top of the uterus. One reason it attaches here is so that it’s out of the way. When it’s at the bottom of the uterus, it can get jostled during sex or by contractions and routine prenatal exams. 

The other reason a placenta attaches to the lower part of the uterus is so it doesn’t cover the opening of the cervix. The cervix connects the uterus to the vagina. During delivery, the cervix widens and flattens so the baby can “exit” the uterus. But this stretching will also tear the placenta.  

Placenta previas are broken down into three “types,” based on how much of the cervix they cover:

• Complete previa is when the placenta covers the entire opening of the cervix.

• Partial previa is when the placenta covers only part of the opening of the cervix.

• Marginal previa is when the placenta is really close to the opening but doesn’t actually cover it.

Who is most likely to develop placenta previa?

Anyone can develop a placenta previa. The condition is extremely common and affects 1 out of every 200 pregnancies. 

The only thing you can do to avoid developing a placenta previa is not smoke before you get pregnant. Otherwise, the situation is out of your control, and there’s nothing you can do to prevent it. 

Like all other medical conditions, placenta previa affects some people more often than others. You are more likely to develop placenta previa if you:

• Had placenta previa during a previous pregnancy

• Had a cesarean section (C-section)

• Had surgery on your uterus (including dilation and curettage, or D&C)

• Got pregnant with the help of in vitro fertilization

• Are older than 35 years old (advanced maternal age)

• Were pregnant with twins or multiples in previous pregnancies

• Have an irregularly shaped uterus

You are less likely to develop placenta previa during your first pregnancy. 

How can you detect placenta previa? 

Your healthcare provider can tell if you have placenta previa during your second trimester ultrasound. Most people get this ultrasound between 18 and 22 weeks of pregnancy. 

During this ultrasound, your provider will look at all of the organs of the fetus as well as your placenta. Using the ultrasound machine, your provider will measure how close your placenta is to your cervix. If they see a placenta previa, they’ll check to see if the placenta is completely or only partially covering your cervix. 

How does a placenta previa affect pregnancy and delivery?

A placenta previa can affect your pregnancy and delivery in a couple of different ways. It can lead to:

• Vaginal bleeding during pregnancy

• Excessive blood loss (hemorrhage) during or after delivery

• Preterm labor and premature birth

The placenta contains many blood vessels, which makes it fragile and easy to tear. When the placenta attaches to the lower part of the uterus, it’s more likely to get stretched and torn. Tearing leads to bleeding, which can be dangerous for you and your fetus.

Vaginal bleeding during pregnancy

The most common symptom of placenta previa is vaginal bleeding during pregnancy. Almost everyone experiences vaginal bleeding at some point if they have placenta previa.

Some people do not experience pain with bleeding, but others may notice cramping. If you have placenta previa and you experience any bleeding, you should see your healthcare provider immediately. 

Even light bleeding can quickly turn into more serious bleeding. You may need medication to help stop the bleeding, which may not stop on its own. Many people need to stay in the hospital for several days to make sure they don’t develop serious bleeding, which can be life-threatening to both you and the developing fetus.

It’s not always obvious why someone with placenta previa develops bleeding. Some people can pinpoint a trigger — like sex or a prenatal exam in which a provider checks the cervix. But often people can’t spot any reason, probably because normal movements or contractions were enough to trigger bleeding. 

Excessive blood loss during or after delivery

Excessive blood loss during or after delivery is the most serious complication of placenta previa. 

During delivery, the uterus starts contracting and the cervix changes shape. These changes can happen quickly and cause rapid tears in the placenta. This type of bleeding can start fast and be hard to control. It’s not common, but this type of hemorrhage can be deadly, even with an experienced healthcare team. 

Some people can also develop placenta accreta, a condition where the placenta gets “stuck” to the uterus. When this happens, the healthcare team can’t easily remove the placenta to stop bleeding. Sometimes the only way to stop the bleeding and save the person’s life is to remove the uterus. 

Placenta previa and accreta are common reasons someone may need an emergency hysterectomy during or right after delivery. 

Preterm labor and delivery

You can experience preterm labor and delivery if you have placenta previa. Many babies who are born prematurely do very well. But, depending on how early they are born, babies can develop long-term health complications. 

If you do not go into preterm labor, your healthcare team will plan to deliver your baby between week 36 and 38 of your pregnancy. The goal is to avoid bleeding and hemorrhage by making sure your baby is delivered before you go into natural labor. This is safer for both you and your baby. 

How do you treat placenta previa?

Unfortunately, there’s no treatment that can change the position of the placenta.

But here’s some good news: Sometimes placenta previa goes away on its own. As the uterus grows during pregnancy, the placenta can move away from your cervix. If a provider notices placenta previa before week 20 of pregnancy, there’s a 90% chance that the placenta will move over time. 

Your placenta previa is less likely to go away if:

• Your placenta hasn’t moved by your third trimester. 

• Your placenta extends over your cervix by more than 2.5 cm in your second trimester.

• Your placenta is attached to the back instead of the front of your uterus.

If you have placenta previa at any point during your pregnancy, you will need to follow up more frequently with your healthcare team. And your provider may ask you to see a specialist team called “maternal-fetal medicine.” 

Your team will continue to measure your placenta with ultrasounds. You may need to limit exercise or avoid standing for more than 4 hours at a time. You’ll also need to avoid any activities that lead to orgasm and any type of vaginal penetration. 

If you develop vaginal bleeding at any point, see your healthcare team immediately. Most people need to stay in the hospital for several days to control the bleeding and make sure it doesn’t come back. You may need blood transfusions if you lose too much blood. Depending on your blood type, you also may need extra RhoGAM shots. 

If your placenta previa does not resolve, you will need a planned delivery before you start week 38 of your pregnancy. You will not be able to go into labor because of the risk of bleeding, which means you will need to have a C-section to deliver your baby. 

For your safety, it’s best to work with an experienced healthcare team. It’s also a good idea to deliver at a facility that has a full neonatal intensive care unit. 

Planning for this type of delivery experience can be scary. But keep in mind that with experienced healthcare teams, most people have safe deliveries and healthy babies. 

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Written by:

Adriena Beatty D.O., MBA, CPE

Adriena Beatty, DO, MBA, CPE, is an Army veteran and board-certified obstetrician and gynecologist with over 20 years of experience. She is a graduate from Tuskegee University with a degree in chemical engineering and chemistry.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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