The placenta nourishes and protects your baby throughout pregnancy, filtering out what she doesn’t need and delivering the oxygen and nutrients she does.
Most of the time, it attaches to the upper part of the uterus. But if it settles in the lower part of the uterus, you might be diagnosed with placenta previa, or your doctor might say you have a low-lying placenta.
- Placenta previa is rare, but serious, and often resolves naturally. Placenta previa occurs in about 1 in 200 pregnancies and involves the placenta covering part or all of the cervix. Many women are diagnosed with a low-lying placenta during the second trimester, but in most cases, it moves upward as the uterus grows, resolving on its own before delivery.
- Vaginal bleeding after 20 weeks is a warning sign. Painless, bright red vaginal bleeding in the second half of pregnancy may indicate placenta previa. While not all women with placenta previa experience bleeding, it is the most common symptom and should be evaluated immediately.
- Delivery options depend on the position of the placenta in late pregnancy. If the placenta still covers or is too close to the cervix later in pregnancy, a scheduled C-section is usually necessary to avoid serious complications. Treatment focuses on monitoring, pelvic rest, and managing symptoms to ensure the pregnancy continues safely for as long as possible.
What is placenta previa?
Placenta previa is a relatively rare pregnancy complication in which the placenta implants low in the uterus and covers part or all of the cervix.[1]
The low position of the placenta results in placental tissue covering the internal cervical os, or the inside the opening of the cervix. That can cause bleeding during pregnancy and labor, and may affect how your baby comes into the world when it's time to deliver.
Because the placenta physically sits on top of the cervix and blocks the opening to the birth canal (the vagina), any case of vaginal bleeding after 20 weeks should raise suspicion of possible placenta previa, if not previously diagnosed.[2]
What’s a low-lying placenta and does it mean I'll have placenta previa?
A placenta that is close to but not covering the cervical opening (when the placental edge is within 2 centimeters) is called a low-lying placenta. During the second trimester of pregnancy, often during your 20-week anatomy scan, your doctor may tell you that you have this condition.
In roughly 9 out of 10 cases, a low-lying placenta resolves on its own and won’t be considered low-lying by the time you give birth. As the baby grows in the third trimester, the uterus expands upward and pulls the placenta higher (up and away from the cervix).
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This “movement” of the placenta will occur in almost all cases of low-lying placentas, making a vaginal delivery safe, but it can also happen in some cases of placenta previa.
If your doctor sees that you have a low-lying placenta in the first or second trimester, they will recommend a follow-up ultrasound between weeks 28 and 32 of pregnancy to check the location of the placenta.
"At [my] 2-week scan, the placenta was showing complete placenta previa," says What to Expect Community mom KarlzAsh. "I had a follow-up scan at 32 weeks, and it’s 4.5 centimeters from the cervix!! Was super pleased, but baby is now breech!"
How common is placenta previa?
Placenta previa occurs in about 1 out of every 200 deliveries.
If you’re told you have a low-lying placenta or placenta previa before 28 weeks, try not to worry. Many women are diagnosed with the condition in the second trimester, usually during a routine ultrasound.
The majority of cases that are diagnosed in the first two trimesters resolve by the third trimester, meaning that the placenta moves up and away from the cervix before delivery.
Who is most at risk of placenta previa?
Placenta previa risk factors include:
- Prior C-section or uterine surgery. Scarring on the uterus due to previous surgeries, including C-sections, uterine fibroid removal and D and C procedures, increases the risk of placenta previa. This risk increases with each subsequent procedure.
- Multiples. Being pregnant with two or more babies increases your likelihood of placenta previa by 40% — there is just a lot more placenta to go around!
- Age. Placenta previa is more likely to occur in women over the age of 30 than in those under the age of 20.
- Second or later pregnancy. The condition is more common in women who have had at least one other pregnancy.
- Smoking or drug use. Cigarette or cocaine use during pregnancy increases your chances of developing a host of complications, including placenta previa.
- Race. Some research suggests that Asian and Black women have a greater risk of placenta previa than other racial groups.
- In vitro fertilization (IVF). Assisted reproductive technology including IVF has been linked to an increased risk of placental problems, including placenta previa.
If you’ve had placenta previa in a past pregnancy, there’s up to an 8% chance you could develop it in your current pregnancy.
The good news is that it won’t impact your chances of getting pregnant again.
Remember, knowledge is power — and peace of mind. The What to Expect app can help you stay informed and connected with other moms-to-be who may be navigating similar concerns.
What are the symptoms of placenta previa?
Placenta previa or a low-lying placenta is usually discovered and diagnosed not on the basis of symptoms but during a routine second-trimester ultrasound.
Sometimes the condition announces itself in the third trimester and occasionally earlier with the following symptoms:
- Bleeding. Placental problems, including placenta previa, are the most common cause of heavy vaginal bleeding in the latter part of pregnancy. About 2 in 3 women with placenta previa experience some painless, bright red bleeding (not just vaginal spotting, which is often normal). However about 1 in 3 women with the condition don’t bleed at all.
- Cramping. While it’s not common to feel pain, some women with placenta previa experience cramping or contractions, though it usually happens in conjunction with bleeding.
- Breech position. Your baby is more likely to be in a breech position when you have placenta previa. That’s because in a typical pregnancy, the most comfortable third trimester position for a baby is head-down at the bottom of the uterus, where there’s the most room. But with placenta previa, the placenta occupies that space where your baby’s head would normally gravitate. That may cause her to stay in (or move to) a breech position.
How can I stop bleeding from placenta previa?
As your cervix begins to dilate and efface in preparation for birth, there may be tearing in the blood vessels that connect the placenta to the uterus in the area over the cervix. This may cause bleeding. The risk of bleeding increases if more of the placenta covers the cervix.
There’s no way to prevent placenta previa, and no surgical or medical procedure can correct the condition. However many bleeding incidents will resolve before blood loss puts you or your baby at risk. Managing light bleeding usually includes avoiding activities that can cause bleeding, like exercise and sex. You’ll also want to avoid using tampons.
Severe and uncontrolled bleeding, especially if your baby is in distress, may be cause for an immediate delivery. Notify your practitioner and head to your labor and delivery unit right away if you experience heavy bleeding.
How is placenta previa treated?
If you’re diagnosed with placenta previa, you'll want to keep a lookout for heavy bleeding as well as signs of preterm labor, which is more common with placenta previa.
Your doctor’s goal is to get you as close to your due date as possible. Once you’ve reached your third trimester, your health care provider may recommend measures to ensure a safe pregnancy and delivery, especially if you experience bleeding. These might include:
- Pelvic rest. This means abstaining from sex, discontinuing any use of tampons or vaginal douches, and foregoing pelvic exams.
- Increased fetal monitoring. Your doctor may want to keep an eye on your baby to make sure her heartbeat remains strong and her movements are consistent.
- Medications. If you present with labor symptoms, your doctor will treat you with medications called tocolytics, which stop early labor and increase the odds that your pregnancy will continue to at least 36 weeks. If you present prior to 34 weeks and there is a risk of delivery, your doctor might recommend treatment with steroids that help premature babies after delivery with complications of prematurity (such as increasing lung maturity). If prenatal testing early on in your pregnancy reveals you’re Rh negative, you may also receive shots of a special Rh-incompatibility treatment known as RhoGAM.
- Bed rest. Because prolonged inactivity can lead to complications including muscle atrophy and increased risk of blood clots, doctors usually avoid prescribing strict bed rest during pregnancy. However your doctor may recommend restricting activity, such as exercise, walking or standing for long periods of time.
- Hospital care. Your practitioner may want you to remain at a hospital until your delivery, particularly if you’ve had a bleeding incident, in order to monitor you and your baby continuously.
Can you deliver naturally with placenta previa?
If the placenta previa resolves and your placenta no longer covers your cervix, it’s possible to deliver vaginally. However, in all cases of persistent placenta previa, women will be scheduled to deliver via C-section.
In women who have a low-lying placenta, if the placenta sits within 1 centimeter of the internal cervical os (or inside the opening of the cervix), the general recommendation is a scheduled C-section because of the high risk of hemorrhage.
In cases where the edge of the placenta sits between 1 and 2 centimeters, that hemorrhage risk decreases, so the possibility of labor and a vaginal delivery exists.
Once the placenta is more than 2 centimeters away from inside the opening of the cervix, there isn’t an increased risk of hemorrhage, so laboring and planning a vaginal delivery is recommended.
“It’s important to weigh those risks and benefits with your provider,” says Shannon Smith, M.D., an OB/GYN and partner at Brigham Faulkner Ob/Gyn Associates in Boston, Massachusetts, and a member of the What to Expect Medical Review Board.
If you haven’t yet reached 34 weeks of pregnancy and preterm delivery is necessary, you’ll receive steroid shots to rapidly mature your baby's lungs before a C-section is performed. If severe bleeding occurs after 36 weeks, your practitioner may recommend an immediate cesarean.
Other placenta previa complications
A placenta previa diagnosis during the third trimester means your practitioner may not be able to stick to your birth plan. While placenta previa itself isn’t dangerous for you or your baby, it can lead to serious bleeding and preterm birth. Your doctor will monitor you closely and take precautions to prevent complications.
Possible complications of placenta previa include:
- Preterm birth. Placenta previa increases the risk of your baby being born before her due date. Preterm delivery, in turn, is linked to babies having a lower birth weight, lower APGAR scores, and neonatal intensive care unit (NICU) stays.
- Placenta accreta. Placenta previa is a risk factor for placenta accreta, which is when the placenta attaches too deeply to the uterine wall. This can cause life-threatening bleeding in the third trimester and at the time of delivery, which is why your doctor will always recommend a scheduled C-section before your due date. The risk is higher with each subsequent C-section.
- Vasa previa. This very rare pregnancy complication, which happens in about 1 in 2,500 pregnancies, occurs when the fetal blood vessels from the placenta cross the opening to the vagina. It’s more common (although still rare) if you have had placenta previa. Because vasa previa can lead to fatal fetal hemorrhage in minutes when the cervix begins dilating and the membranes rupture, your doctor will plan for an early cesarean delivery and likely a prolonged hospitalization prior.
- Hemorrhage and hysterectomy. If you have placenta previa, bleeding can sometimes become uncontrolled during labor or in the hours following delivery. In rare cases, severe bleeding may require a blood transfusion, uterine artery embolization and/or hysterectomy (i.e., removal of the uterus).
- Increased risk in future pregnancies. Having placenta previa during pregnancy increases the risk of having placenta previa and preterm birth in future pregnancies.
Since you’ll be on vigilant lookout for symptoms and you know to seek immediate treatment if you bleed, you and your baby should be okay. The most important thing to keep in mind: The vast majority of women with low-lying placenta or placenta previa safely deliver healthy babies.
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