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Placenta Previa

Reviewed by James Brann, M.D.

Painless Bleeding in Pregnancy is a Sign of Placenta Previa

Learn about placenta previa.

Vaginal bleeding at any stage of pregnancy can make you nervous, but in the third trimester, painless bleeding can sometimes be a sign of placenta previa - a pregnancy complication in which your placenta is attached to the lower portion of your uterus, and it covers either partially or completely the opening of your uterus, called the cervix.

Your placenta is the life-support organ for your baby. Not only does it supply your growing baby with oxygen and nutrients, but it also removes wastes. The placenta is part of your afterbirth and it is delivered after your baby is born. During labor and delivery, your baby will make his or her exit through the cervix into the vagina.

In early pregnancy, it is normal for your placenta to develop and attach low in your uterus. But as you continue your pregnancy, the expanding uterus will pull your placenta upwards, away from the cervical opening.

When the placenta remains in the lower part of your uterus, it is called a placenta previa, and this can create complications for the pregnancy.

There are Three Types of Placenta Previa:

  • Complete previa -- Your placenta completely covers the opening of your uterus. It is estimated that 20 to 30 percent of placenta previas are this type.

  • Marginal previa -- Your placenta lies adjacent but does not cover the opening of your uterus.

  • Partial previa -- Your placenta partially covers the opening of your uterus.

Risk factors of developing placenta previa:

  • Prior placenta previa.

  • Previous cesarean delivery. In fact, after four c-sections, you are at a 10 percent increased risk for placenta previa.

  • Advanced maternal age (over 35). Your risk for this complication increases with age.

  • Prior surgery on your uterus that resulted in endometrial scarring.

  • Smoking during pregnancy.

  • Cocaine use during pregnancy.

  • Carrying twins or multiples. When compared to women with single babies, being pregnant with multiples increases your risk for placenta previa.

Placenta previa occurs in 4 out of every 1,000 pregnancies. In the second trimester, you may be diagnosed with a low-lying placenta. This means that the edge of your placenta lies within 2 or 3 centimeters of the opening of the uterus but not bordering it.

Fortunately, in many cases of low-lying placenta, the problem will resolve on its own as the pregnancy continues. In fact, 90 percent of low-lying placentas that are found with ultrasound before week 20 of pregnancy will go away by the end of your pregnancy.

Painless vaginal bleeding in the third trimester is the most common sign of placenta previa. Most often, this bleeding occurs when the cervix begins to thin and dilate to prepare for labor. The bleeding can be so severe that it places both mother and baby's lives in danger.

Occasionally, you may experience uterine cramping with the bleeding. The bleeding can stop suddenly but it may start again days or weeks later. Bleeding from placenta previa usually occurs during the labor process, but sometimes it can occur before the onset of labor.

Luckily, with regular prenatal care, placenta previa is almost always detected with ultrasound. Once you are diagnosed, your doctor or healthcare provider will monitor you closely and educate you on possible complications you may expect.

Possible complications due to placenta previa include life-threatening hemorrhage (major bleeding) and preterm labor and delivery (giving birth to a baby before 37 weeks).

You're also at an increased risk for infection, blood clots, and placenta accreta (a pregnancy complication that occurs when your placenta implants into the uterine wall.

Unfortunately, placenta previa cannot be prevented but the complications can be managed.

In many cases, you may be placed on bed rest. You should also avoid using tampons, douching, or placing anything in your vagina.

If you experience heavy bleeding due to placenta previa, you may need to be admitted to the hospital for monitoring. If you've lost a lot of blood, you may need a blood transfusion. If the bleeding is very heavy or life threatening, an emergency cesarean will be done, regardless of how far along the pregnancy is, to save your life.

If you end up delivering early due to your placenta previa, your premature baby may be at risk for certain health issues after birth. However, medical advances in neonatal care allow doctors to save younger and younger babies. In fact, babies born at 26 weeks have an 80 percent survival rate!

Always call your healthcare provider if you experience any kind of bleeding during pregnancy. It is always better to be safe than sorry.

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