The placenta attaches to the wall of the uterus (womb) and supplies the baby with food and oxygen through the umbilical cord. Placenta previa is a condition in which the placenta lies very low in the uterus and covers all or part of the cervix. The cervix is the opening to the uterus that sits at the top of the vagina.
Placenta previa happens in about 1 in 200 pregnancies. If you have placenta previa early in pregnancy, it usually isn’t a problem. However, it can cause serious bleeding and other complications later in pregnancy.
Normally, the placenta grows into the upper part of the uterus wall, away from the cervix. It stays there until your baby is born. During the last stage of labor, the placenta separates from the wall, and your contractions help push it into the vagina (birth canal). This is also called the afterbirth.
During labor, your baby passes through the cervix into the birth canal. If you have placenta previa, when the cervix begins to efface (thin out) and dilate (open up) for labor, blood vessels connecting the placenta to the uterus may tear. This can cause severe bleeding during labor and birth, putting you and your baby in danger.
The most common symptom of placenta previa is painless bleeding from the vagina during the second half of pregnancy. Call your health care provider right away if you have vaginal bleeding anytime during your pregnancy. If the bleeding is severe, go to the hospital.
Not all women with placenta previa have vaginal bleeding. In fact, about one-third of women with placenta previa don’t have this symptom.
An ultrasound usually can find placenta previa and pinpoint the placenta’s location. In some cases, your provider may use a transvaginal ultrasound instead.
Even if you don’t have vaginal bleeding, a routine, second trimester ultrasound may show that you have placenta previa. Don’t be too worried if this happens. Placenta previa found in the second trimester fixes itself in most cases.
Treatment depends on how far along you are in your pregnancy, the seriousness of your bleeding and the health of you and your baby. The goal is to keep you pregnant as long as possible. Providers recommend cesarean birth (c-section) for nearly all women with placenta previa to prevent severe bleeding.
If you are bleeding as a result of placenta previa, you need to be closely monitored in the hospital. If tests show that you and your baby are doing well, your provider may give you treatment to try to keep you pregnant for as long as possible.
If you have a lot of bleeding, you may be treated with blood transfusions. A blood transfusion is having new blood put into your body. Your provider also may give you medicines called corticosteroids. These medicines help speed up development of your baby’s lungs and other organs.
Your provider may want you to stay in the hospital until you give birth. If the bleeding stops, you may be able to go home. If you have severe bleeding due to placenta previa at about 34 to 36 weeks of pregnancy, your provider may recommend an immediate c-section.
At 36 to 37 weeks, your provider may suggest an amniocentesis to test the amniotic fluid around your baby to see if her lungs are fully developed. If they are, your provider may recommend an immediate c-section to avoid risks of future bleeding.
At any stage of pregnancy, a c-section may be necessary if you have dangerously heavy bleeding or if you and your baby are having problems.
We don’t know what causes placenta previa. However, you may be at higher risk for placenta previa if:
- You smoke cigarettes.
- You use cocaine.
- You’re 35 or older.
- You’ve been pregnant before.
- You’re pregnant with twins, triplets or more.
- You’ve had surgery on your uterus, including a c-section or a D&C (dilation and curettage). A D&C is when a doctor removes tissue from the lining of a woman's uterus. Some women have a D&C after a miscarriage.
If you’ve had placenta previa in a past pregnancy, you have a 2 to 3 in 100 (2 to 3 percent) chance of having it again.
We don’t know how to prevent placenta previa. But you may be able to reduce your risk by not smoking and not using cocaine. You also may be able to lower your chances of having placenta previa in future pregnancies by having a c-section only if it’s medically necessary. If your pregnancy is healthy and there are no medical reasons for you to have a c-section, it’s best to let labor begin on its own. The more c-sections you have, the greater your risk of placenta previa.
Last reviewed January 2012
See also: Placental abruption, Placental accreta, increta and percreta
Frequently Asked Questions
What is mononucleosis?
Mononucleosis (also called mono) is an infection usually caused by the Epstein-Barr virus (EBV). It’s sometimes caused by another virus called cytomegalovirus (CMV). EBV and CMV are part of the herpes virus family. Mono is most common in teenagers and young adults, but anyone can get it. Mono is called the “kissing disease” because it’s usually passed from one person to another through saliva. In addition to kissing, it can also be passed through sneezing, coughing or sharing pillows, drinks, straws, and toothbrushes.
You can have mono without having any symptoms. But even if you don’t get sick, you can still pass it to others. Symptoms can include:
- Achy muscles
- Belly pain
- Fatigue (feeling tired all the time)
- Sore throat
- Swollen glands in your neck
If your symptoms don’t go away or get worse, tell your health care provider. He’ll most likely do a physical exam and test your blood to find out for sure if you have mono.
There’s no vaccine to prevent mono. There’s also no specific treatment. The best care is to take it easy and get as much rest as you can. It may take a few weeks before you fully recover.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
I had a miscarriage. How long should I wait to try again?
Before getting pregnant again, it's important that you are ready both physically and emotionally. If you don't need tests or treatments to discover the cause of the miscarriage, it's usually OK for you to become pregnant after one normal menstrual cycle. However, it may take longer for you to feel emotionally ready to be pregnant again. Everyone responds differently to a miscarriage. Only you will know when you are ready to try to get pregnant again.
Are gallstones common during pregnancy?
Not common, but they do happen. Elevated hormones during pregnancy can cause the gallbladder to function more slowly, less efficiently. The gallbladder stores and releases bile, a substance produced in the liver. Bile helps digest fat. When bile sits in the gallbladder for too long, hard, solid nuggets called gallstones can form. The stones can block the flow of bile, causing indigestion and sometimes serious pain. Staying at a healthy weight during pregnancy can help lower your risk of gallstones. Exercise and eating foods that are low in fat and high in fiber, like veggies, fruits and whole grains, can help, too. Symptoms of gallstones include nausea, vomiting and intense, continuous abdominal pain. Treatment during pregnancy may include surgery to remove the gallbladder. Gallstones in the third trimester can be managed with a strict meal plan and pain medication, followed by surgery several weeks after delivery.