While several complications can occur during pregnancy, most women will not experience major problems. Your health care team will work with you to ensure that your pregnancy goes smoothly. However, it is important to be aware of what can happen, so you know when to talk to your doctor about symptoms or other concerns.
Placenta previa is one such complication. It is usually detected by ultrasound during routine prenatal checkups, and many cases resolve on their own by the third trimester. However, placenta previa can affect how your team cares for you during pregnancy and delivery.
Read on to learn what placenta previa is, what its risk factors are, how it is identified, and what treatment to expect if you are diagnosed.
Placenta previa is a problem with the position of the placenta that can cause major complications during pregnancy.
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 occurs when the placenta attaches low enough in the uterus to cover all or part of the cervix. It affects about 11% of pregnancies at 20 weeks gestation, but only continues into the third trimester in about 0.3-2% of those cases, with the remainder resolving on their own. Placenta previa can cause significant problems during pregnancy, including:
- Bleeding, which is a serious symptom that requires expert evaluation.
- Early separation of the placenta from the wall of the uterus, which can cause significant bleeding and require premature delivery.
- Premature birth or low birth weight in cases of premature delivery.
Causes of placenta previa
The exact cause of placenta previa is not 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 to implant and begin growing. Therefore, if there is scarring near the cervix, an egg may implant there instead of in a more normal position higher up in the uterus.
Placenta previa may not present symptoms
Most cases of placenta previa are diagnosed early in pregnancy during ultrasounds. Because most cases resolve by the third trimester, the condition is often asymptomatic. In the small percentage of cases that persist, the main symptom is usually painless, bright red vaginal bleeding. Occasionally, this may be accompanied by uterine contractions.
Tell your doctor right away if you have vaginal bleeding at any time during pregnancy. If the bleeding is heavy, 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 is associated with certain pregnancy characteristics and risk factors, including:
- Previous pregnancies
- Placenta previa in a previous pregnancy
- Cesarean delivery in a previous pregnancy
- Being pregnant with multiples (such as twins or triplets)
- Using assisted reproductive technology, such as in vitro fertilization (IVF)
- Uterine scars or history of uterine procedures.
- Be 35 years of age or older
- Smoking tobacco
- Cocaine use
How is placenta previa diagnosed?
Placenta previa is usually diagnosed by abdominal ultrasound during the second or third trimester. About 90% of cases get better on their own. This is because the placenta can gradually grow into a more normal position, where there is a better blood supply.
How placenta previa is managed and treated
If you are diagnosed with placenta previa, your care team will ask you to reduce your overall activity. If it persists into the third trimester, you may be asked to avoid sexual activity, moderate to vigorous exercise, lifting more than 20 pounds, and standing for long periods of time. Your care team will also ask you to have more frequent ultrasounds to monitor the development of the placenta. If you stop covering your cervix, you may be able to have a vaginal birth.
However, if the placenta remains close to the cervix, it may stretch due to the changes the cervix undergoes to prepare for delivery. This stretching creates a risk of heavy bleeding during vaginal delivery, so if the placenta continues to block the cervix, your doctor will talk to you about cesarean delivery and what to expect before delivery.
The main treatment for unresolved placenta previa is a cesarean section.
Almost all cases of placenta previa that do not resolve by the third trimester are treated by cesarean delivery. If you need a cesarean delivery, your doctor will schedule your delivery around week 36 or 37 of pregnancy, possibly sooner if your situation warrants it. The goal of your care team will be to help you complete as much of your pregnancy as possible.
If you have 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 is time to deliver. Otherwise, your doctor may prescribe corticosteroids to speed up your baby’s lung development and magnesium sulfate to protect your baby’s brain. Depending on the amount of bleeding, you may receive blood transfusions.
Tell your care team if you have risk factors or symptoms of placenta previa.
Prenatal care visits are one of the best tools to help you stay safe and healthy during pregnancy. They are opportunities for your care team to detect problems like placenta previa early and help manage your risk of complications. The more information they have, the better they can care for you. Let your care team know if you have any risk factors they don’t know about or if you’re concerned about any symptoms you’re experiencing.
Note: Talk to your doctor right away if you experience vaginal bleeding at any time during pregnancy. Call 911 or go to a hospital if the bleeding is heavy.
