Placenta Previa

Placenta previa If you have placenta previa, it means that your placenta is lying unusually low in your uterus, next to or covering your cervix. The placenta is the pancake-shaped organ — normally located near the top of the uterus — that supplies your baby with nutrients through the umbilical cord. Placenta previa is not usually a problem early in pregnancy. But if it persists into later pregnancy, it can cause bleeding, which may require you to deliver early and can lead to other complications. If you have placenta previa when it's time to deliver your baby, you'll need to have a c-section. If the placenta covers the cervix completely, it's called a complete or total previa. If it's right on the border of the cervix, it's called a marginal previa. (You may also hear the term "partial previa," which refers to a placenta that covers part of the cervical opening once the cervix starts to dilate.) If the edge of the placenta is within 2 centimeters of the cervix but not bordering it, it's called a low-lying placenta. The location of your placenta will be checked during your midpregnancy ultrasound exam.

Pathophysiology No specific cause of placenta previa has yet been found but it is hypothesized to be related to abnormal vascularisation of the endometrium caused by scarring or atrophy from previous trauma, surgery, or infection. In the last trimester of pregnancy the isthmus of the uterus unfolds and forms the lower segment. In a normal pregnancy the placenta does not overlie it, so there is no bleeding. If the placenta does overlie the lower segment, it may shear off and a small section may bleed. Women with placenta previa often present with painless, bright red vaginal bleeding. This bleeding often starts mildly and may increase as the area of placental separation increases. Praevia should be suspected if there is bleeding after 24 weeks of gestation. Abdominal examination usually finds the uterus non-tender and relaxed. Leopold's Maneuvers may find the fetus in an oblique or breech position or lying transverse as a result of the abnormal position of the placenta. Praevia can be confirmed with an ultrasound. In parts of the world where ultrasound is unavailable, it is not uncommon to confirm the diagnosis with an examination in the surgical theatre. The proper timing of an examination in theatre is important. If the woman is not bleeding severely she can be managed non-operatively until the 36th week. By this time the baby's chance of survival is as good as at full term. Placenta previa is classified according to the placement of the placenta: •

Type I or low lying: The placenta encroaches the lower segment of the uterus but does not infringe on the cervical os.

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Type II or marginal: The placenta touches, but does not cover, the top of the cervix.

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Type III or partial: The placenta partially covers the top of the cervix

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Type IV or complete: The placenta completely covers the top of the cervix

Placenta previa is itself a risk factor of placenta accreta.

What causes placenta previa, and how can you lower your risk? Doctors aren't sure what causes placenta previa. But there are things that raise a woman’s risk of it. These things are called risk factors. Some risk factors you can control to lower your risk. Others are things you can't control.

Risk factors for placenta previa that you can control include: •

Smoking during pregnancy.

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Using cocaine during pregnancy.

Risk factors that you can't control include:

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Past surgeries or tests that affected the lining of the uterus, such as uterine surgery, dilation and curettage (D&C), or myomectomy.

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Past cesarean delivery (C-section).

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A history of five or more past pregnancies.

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Being 35 or older.

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A history of a past placenta previa.

If your doctor finds out before your 20th week of pregnancy that you have a placenta that is attached low in the uterus, chances are good that it will get better on its own. In fact, 9 out of 10 cases found before the 20th week will go away on their own by the end of the pregnancy.1 This is because as the lower uterus grows, the position of the placenta can change. So by the end of the pregnancy, the placenta may no longer block the cervix.

What are the symptoms? Some women with placenta previa do not have any symptoms. But there are a few warning signs. If you have placenta previa, you may notice one or more symptoms. These include: •

Sudden, painless vaginal bleeding that is light to heavy. The blood is often bright red.

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Symptoms of early labor, such as regular contractions and aches or pains in your lower back or belly.

Call your doctor or go to the nearest emergency room right away if you have: •

Medium to severe vaginal bleeding during the first trimester.

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Any vaginal bleeding in the second or third trimesters.

How is placenta previa diagnosed? Most cases of placenta previa are found during the second trimester when a woman has a routine ultrasound. Or it may be found when a pregnant woman has vaginal bleeding and gets an ultrasound to find out what is causing it. Some women find out that they have placenta previa only when they have bleeding at the start of labor.

How is it treated? The kind of treatment you will have depends on: •

How much you are bleeding.

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How the problem is affecting your health and your baby’s health.

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How close you are to your due date.

If you have placenta previa and aren't bleeding, it is important to avoid having sex or vaginal exams and to avoid putting anything else in your vagina. (But you may have a carefully done vaginal exam at the hospital.) You should see your doctor if you have any bleeding. If you are bleeding, you may have to stay in the hospital. When your baby is mature enough, or if too much bleeding is putting you or your baby in danger, your baby will be delivered. Doctors always do a cesarean section when there is a placenta previa. This is because the placenta can be disturbed with a vaginal delivery, and it can cause severe bleeding. What are the possible problems from having placenta previa? Placenta previa can cause problems for both the mother and the baby. These include: •

A condition called placenta abruptio. This means that the placenta breaks away from the wall of the uterus before the baby has been born.

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Severe bleeding in the mother before or during delivery. This can be very dangerous for both the mother and the baby. If the placenta has attached or grown into the wall of the uterus (known as placenta accreta, placenta increta, or placenta percreta), the bleeding can be heavy enough to require a hysterectomy.2

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Having to deliver the baby too early.

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Birth defects. These occur more often in pregnancies with placenta previa than in pregnancies without this problem.

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.

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Premature birth. Severe bleeding may prompt an emergency C-section before your baby is full term.

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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). Tests and Diagnoses

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: Treatments and drugs Treatment for placenta previa depends on various factors, including: •

The amount of vaginal bleeding

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Whether the bleeding has stopped

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Your baby's gestational age

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Your health

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Your baby's health

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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. •

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.

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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. Coping and support

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.

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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.

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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 thankyou notes.

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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.