Placenta previa: Signs, risk factors and treatments for a low-lying placenta

Even though there are a number of complications that can occur during pregnancy, most people won’t experience significant issues. And your care team will be working with you to help ensure your pregnancy is a smooth one. But it’s still important to be aware of what can happen, so you know when to speak with your doctor about symptoms or other concerns.

Placenta previa is one such complication. It’s typically detected by ultrasound exams during routine prenatal appointments, and many cases resolve on their own by the third trimester. However, placenta previa may affect how your team cares for you during pregnancy and delivery.

Keep reading to learn what placenta previa is, what its risk factors are, how it’s identified and what treatment to expect if you’re diagnosed.

Placenta previa is an issue with the placenta’s position that may cause significant pregnancy complications

The placenta – the organ that forms during pregnancy to provide oxygen and nutrients to the baby – normally attaches to the side or top of the uterus. Placenta previa is a condition that happens when the placenta attaches low enough in the uterus to cover all or part of the cervix. It affects around 11% of pregnancies at 20 weeks of gestation, but only continues into the third trimester in about 0.3-2% of those cases, with the rest resolving on their own. Placenta previa can cause significant issues during pregnancy, including:

• Bleeding, which is a serious symptom that requires an expert’s evaluation.
• Early separation of the placenta from the wall of the uterus, which can cause significant bleeding and require an early delivery.
• Premature birth or low birth weight in cases of early delivery.

Causes of placenta previa

The exact cause of placenta previa isn’t well understood. Studies have suggested that it may be associated with damage to the uterine lining. Scars in the uterus are rich in oxygen and collagen, which a fertilized egg needs in order to implant itself and start growing. So if there’s scarring near the cervix, an egg may implant there instead of in a more normal position higher in the uterus.

Placenta previa may not have symptoms

The majority of placenta previa cases are diagnosed early in pregnancy during ultrasounds. Since most cases resolve by the third trimester, the condition frequently has no symptoms. In the small percentage of cases that continue, the primary symptom is typically bright red, painless vaginal bleeding. Occasionally, this may be paired with uterine contractions.

Tell your doctor immediately if you have vaginal bleeding at any point during pregnancy. If the bleeding is severe, call 911 or go to a hospital.

How to know if you are at risk for placenta previa

Although the exact cause of placenta previa is unknown, studies have shown that it’s associated with certain pregnancy characteristics and risk factors. These include:

• Previous pregnancies
• Placenta previa in a previous pregnancy
• Cesarean delivery (C-section) in a previous pregnancy
• Being pregnant with multiples (such as twins or triplets)
• Using assisted reproductive technology, such as in-vitro fertilization (IVF)
• Uterine scarring or a history of uterine procedures
• Being 35 years of age or older
• Smoking tobacco
• Using cocaine

How is placenta previa diagnosed?

Placenta previa is usually diagnosed with an abdominal ultrasound during the second or third trimester. About 90% of cases get better on their own. This is because the placenta may gradually grow towards a more normal position where there’s a better blood supply.

How placenta previa is monitored and treated

If you’re diagnosed with placenta previa, your care team will ask you to reduce your overall activity. If it persists into the third trimester, they may ask you to avoid sexual activity, moderate to intense exercise, lifting more than 20 pounds and standing for long periods of time. Your care team will also have you come in for more frequent ultrasounds in order to track your placenta’s development. If it stops covering the cervix, you may be able to have a vaginal delivery.

However, if the placenta stays near the cervix, it may be stretched by the changes the cervix goes through to prepare for labor. This stretching creates a risk of severe bleeding during vaginal delivery, so if your placenta continues to block your cervix, your doctor will talk with you about delivering by C-section and what to expect leading up to it.

The main treatment for unresolved placenta previa is a C-section

Nearly all cases of placenta previa that don’t resolve by the third trimester are treated via C-section. If you need a C-section, your doctor will schedule the delivery for around week 36-37 of pregnancy – possibly earlier if your situation requires it. Your care team’s goal will be to help you complete as much of the pregnancy as possible.

If you experience vaginal bleeding, you may be asked to stay in the hospital for closer monitoring. If the bleeding stops, you may be able to go home until it’s time to deliver. Otherwise, your doctor might prescribe corticosteroids to speed up your baby’s lung development and magnesium sulfate to protect their brain. Depending on the amount of bleeding, you may receive blood transfusions.

Let your care team know if you have risk factors or symptoms of placenta previa

Your prenatal care visits are one of your best tools for staying safe and healthy throughout pregnancy. They’re opportunities for your care team to detect issues like placenta previa early and help control your risk of complications. The more information they have, the better they can care for you. Let your care team know if you have risk factors they’re unaware of or if you’re concerned about any symptoms you’re experiencing.

Note: Talk with your doctor immediately if you experience vaginal bleeding at any point during your pregnancy. Call 911 or go to a hospital if the bleeding is severe.