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Placenta previa is an uncommon pregnancy complication that can cause excessive bleeding before or during delivery.

Soon after conception, the placenta begins to form. This oval, flat organ provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. It attaches to the wall of your uterus, and your baby's umbilical cord arises from it, forming a vital connection between you and your baby.

Placenta previa occurs when the placenta attaches to the lower part of your uterine wall, partially or totally covering your cervix. When the cervix starts to open in preparation for labor, the placenta is detached, which can trigger severe vaginal bleeding. Thankfully, placenta previa is nearly always detected before a woman or her baby is in significant danger.

Painless, bright red vaginal bleeding in the second half of pregnancy is the main sign of placenta previa.

Although some women have light bleeding or spotting during the first trimester or early second trimester, bleeding associated with placenta previa usually occurs near the end of the second trimester or the beginning of the third. The amount of bleeding may range from light to heavy. And it usually stops, but it nearly always recurs days or weeks later. Some women who have placenta previa experience contractions with the bleeding.

Types of placenta previa
There are three specific types of placenta previa:

• Total placenta previa. In total placenta previa, the placenta completely covers the cervix.
• Partial placenta previa. In partial placenta previa, the placenta partly covers the cervix.
• Marginal placenta previa. In marginal placenta previa, the placenta approaches the edge of the cervix.

Low-lying placenta is a term used to describe a placenta that lies low in the uterus but isn't quite close enough to the cervix to qualify as marginal placenta previa. This condition usually doesn't cause signs or symptoms during pregnancy, but it may cause bleeding after delivery.

When to see a doctor
If you're pregnant, seek regular prenatal care. If you experience any vaginal bleeding during your second or third trimester, call your health care provider right away. Your health care provider will likely do an ultrasound to determine the source of the bleeding.

If you've been diagnosed with placenta previa, make sure that any health care provider you see during pregnancy is aware of the condition. Examining the cervix can lead to heavy bleeding. Sex is also off-limits for the rest of the pregnancy.

Early in pregnancy, the placenta may implant in the lower part of the uterus. As the uterus grows, the placenta usually moves up and away from the opening of the uterus (cervix). If it doesn't, the cervix may be blocked. This is placenta previa.

Placenta previa is associated with:

• Scars in the lining of the uterus (endometrium)
• A large placenta, such as with a multiple pregnancy
• An abnormally shaped uterus

Placenta previa is more common among women who:

• Have already delivered at least one baby
• Had a previous C-section
• Had placenta previa with a previous pregnancy
• Are age 35 or older
• Are Asian
• Smoke
• Are carrying twins, triplets or other multiples
• Have had a previous uterine surgery, such as myomectomy to remove uterine fibroids or dilation and curettage (D and C) to scrape the uterine lining

If you have placenta previa, your health care provider will monitor you and your baby carefully to reduce the risk of these serious complications:

• Bleeding. One of the biggest concerns with placenta previa is the risk of severe vaginal bleeding (hemorrhage) during labor, delivery or the first few hours after delivery. The bleeding can be heavy enough to cause maternal shock or even death.
• Premature birth. Severe bleeding may prompt an emergency C-section before your baby is full term.
• Placenta accreta. If the placenta implants too deeply and firmly into the uterine wall, the placenta may not spontaneously detach from the uterus after delivery — an uncommon condition known as placenta accreta. This can result in severe bleeding and, often, the need for surgical removal of the uterus (hysterectomy).

If you're pregnant beyond 12 to 13 weeks' gestation and develop any vaginal bleeding, call the doctor who is caring for you during pregnancy (obstetrical care provider). Depending on your symptoms, your personal health history and how far along you are in the pregnancy, your doctor may recommend immediate medical care. But don't panic. If you have placenta previa, it can be managed with a good outcome for both you and your baby 90 percent of the time.

Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Ask about pre-appointment restrictions. In most cases you'll be seen immediately. However, if your appointment will be delayed for a day or two, ask whether you should restrict your activity while you wait to come in.
• Share your medical history. Depending on your prior care, your doctor likely will already know important medical details about this pregnancy and much of your reproductive history. But if you haven't yet told your doctor about previous uterine surgeries, including dilation and curettage (D and C) following a miscarriage or abortion, it's important for your health and your baby's health to share this information now.
• Find a family member or friend who can join you for your appointment. The fear you may be feeling about bleeding during pregnancy can make it difficult to focus on what the doctor says. Take someone along who can help soak up all the information.
• Write down questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.

Below are some basic questions to ask your doctor about placenta previa. If any additional questions occur to you during your visit, don't hesitate to ask.

• Do I have placenta previa?
• Is there a chance it could resolve on its own?
• What treatment approach do you recommend?
• What follow-up care will I need for the rest of my pregnancy?
• Is there anything I can do to help prolong my pregnancy?
• Do I need to be on bed rest? For how long?
• What signs or symptoms, if they occur, should cause me to call you?
• What signs or symptoms, if they occur, should cause me to go to the hospital?
• Will I be able to deliver vaginally?
• Does this condition increase the risk of complications during future pregnancies?
• Am I at risk of placenta accreta?

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to talk about in-depth. Your doctor may ask:

• When did you first notice vaginal bleeding?
• Did you bleed only once, or has the bleeding come and gone?
• How heavy is the bleeding?
• Is the bleeding accompanied by any pain or contractions?
• Have you had any previous pregnancies that I'm not aware of?
• Have you had any uterine surgeries that I'm not aware of, including C-section, fibroid removal or dilation and curettage (D and C) after a miscarriage or abortion?
• Do you or did you smoke? How much?
• How far do you live from the hospital?
• How long would it take to get to the hospital in an emergency, including time to arrange child care, transportation, etc.?
• Do you have friends or family nearby who could care for you if you need bed rest?

Placenta previa is diagnosed through ultrasound, either during a routine prenatal appointment or after an episode of vaginal bleeding. Placenta previa is nearly always detected before a woman or her baby is in significant danger.

Diagnosis before 20 weeks of pregnancy
It's not unusual to detect a low-lying placenta or to see the placenta covering the cervix during a routine midpregnancy ultrasound. Most of these cases resolve on their own before delivery, as the uterus grows and the placenta migrates away from the cervix. You may need additional ultrasounds to track the position of your placenta. The longer placenta previa persists, the more likely it will be present at delivery.

Diagnosis after 20 weeks of pregnancy
Your health care provider may detect placenta previa later in pregnancy during an ultrasound for an unrelated reason. At this stage of pregnancy, however, vaginal bleeding is usually the tip-off.

If you experience vaginal bleeding during the second or third trimester, call your health care provider right away. You'll likely need to go to your doctor's office or the hospital to determine the cause of the bleeding. In most cases, your health care provider can use an abdominal ultrasound to quickly confirm or rule out placenta previa.

A definitive diagnosis may require a combination of abdominal ultrasound and transvaginal ultrasound, which is done through a wand-like device (transducer) placed inside your vagina. Your health care provider will closely monitor the location of the transducer in your vagina to prevent any bleeding. Rarely, magnetic resonance imaging (MRI) may be used to diagnose placenta previa.

If your health care provider suspects that you may have placenta previa, he or she will avoid routine vaginal exams to reduce the risk of heavy bleeding. You may need additional ultrasounds or, rarely, an MRI to determine the exact location of your placenta before delivery. Your baby's heartbeat may be tracked as well.

Related conditions
Two uncommon conditions are often grouped with placenta previa because they can cause vaginal bleeding in the late second or third trimester. If you have vaginal bleeding late in your pregnancy, your health care provider will also consider these conditions before making a diagnosis:

• Placental abruption. Rarely, the placenta separates from the uterus before birth. This can deprive the baby of oxygen and nutrients and cause heavy bleeding that may be dangerous for both mother and baby.
• Vasa previa. The umbilical cord usually develops in the center of the placenta. If the umbilical cord attaches to the placenta in an unusual way, a portion of the blood vessels normally inside the umbilical cord may be left unprotected. If these unprotected blood vessels cross the cervix, it's known as vasa previa. If these blood vessels rupture, the baby faces life-threatening bleeding.

Treatment for placenta previa depends on various factors, including:

• The amount of vaginal bleeding
• Whether the bleeding has stopped
• Your baby's gestational age
• Your health
• Your baby's health
• The position of the placenta and the baby

For little or no bleeding
If you have marginal placenta previa or another form of placenta previa but little or no bleeding, your health care provider may recommend bed rest at home. Depending on the circumstances, you may need to lie in bed most of the time —sitting and standing only when necessary. You'll need to avoid sex and vaginal exams, which can trigger bleeding. Exercise is usually off-limits, too. Discuss the do's and don'ts with your health care provider — and be prepared to seek emergency medical care if you begin to bleed.

If your placenta doesn't cover your cervix, you may be allowed to attempt a vaginal delivery. If you begin to bleed heavily, you may need an emergency C-section.

For heavy bleeding
If you're bleeding, you may need bed rest in the hospital. If the bleeding is severe, you may need a blood transfusion to replace lost blood. You may also benefit from medications to prevent premature labor.

Your health care provider will likely plan a C-section as soon as the baby can be safely delivered, ideally after 36 weeks of pregnancy. If it's not possible to wait, you will need an earlier C-section. In this case, you may be given corticosteroids to speed your baby's lung development. In as little as 48 hours, these potent medications can help your baby's lungs prepare for life outside the uterus.

For bleeding that won't stop
If your bleeding can't be controlled or your baby is in distress, you may need an emergency C-section — even if the baby is premature.

Pregnancy is supposed to be a time of awe and anticipation. If you're diagnosed with placenta previa, you're sure to be worried about how your condition will affect your baby. Some of these strategies may help:

• Learn about placenta previa. Gathering information about your condition may help you feel less scared. Talk to your health care provider, do some research on your own and connect with other women who've had placenta previa.
• Prepare for a C-section. Placenta previa may prevent you from delivering your baby vaginally. Ask your health care provider every C-section question that comes to mind. If you're disappointed that you may not have a vaginal birth, remind yourself that your baby's health and your health are more important than the method of delivery.
• Make the best of bed rest. If your health care provider recommends bed rest, fill your days by planning for your baby's arrival. Read about newborn care or purchase newborn necessities, either online or from catalogs. Or use the time to balance your checkbook, organize old photo albums or catch up on thank-you notes.
• Take care of yourself. Surround yourself with things that bring you comfort, such as a good book or a favorite pair of pajamas. Give your partner, friends and loved ones concrete suggestions for ways to help, such as bringing a favorite food or simply stopping by for a visit.

A condition that could cause excessive bleeding before or during delivery isn't part of any mother's vision of the perfect pregnancy. Yet most women who have placenta previa go on to deliver a healthy baby — which is far better than a perfect pregnancy.