Placenta previa happens when the placenta lies low in the uterus and covers all or part of the opening to the vagina.
If you develop the condition early in your pregnancy, it usually isn’t a problem since the placenta grows upward with the uterus during pregnancy.
If you develop the condition later in pregnancy and the birth canal is blocked it can cause serious bleeding and may prevent vaginal delivery.
Talk with your providers about ways to deal with placenta previa, which could include having a planned c-section (caesarean birth).
The placenta attaches to the wall of the womb (uterus) 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 opening to the cervical opening 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 because it may resolve as the pregnancy grows. However, if it persists 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, after the baby is born the placenta separates from the wall, and your contractions help push it into the birth canal (vagina). 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 thin out (efface) and open up (dilate), 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.
If a placenta previa is identified by ultrasound and appears to block the cervix, no vaginal exams are performed and an elective c-section is planned.
What causes placenta previa?
No one knows what causes placenta previa. However, you may be at higher risk for placenta previa if you:
- Have had a c-section in the past.
- Have had in vitro fertilization for infertility.
- Smoke cigarettes.
- Use cocaine.
- Are 35 or older.
- Have been pregnant before.
- Are pregnant with twins, triplets or more.
- Have had placenta previa in an earlier pregnancy.
- Have had surgery on your internal reproductive organs, such as myomectomy or tissue removal from the lining of your uterus (this is also called dilation and curettage or D&C). Some people have a D&C after miscarriage.
If you’ve had placenta previa before, what are your chances of having it again?
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.
What are the symptoms of placenta previa?
Most of the time, placenta previa has no symptoms; it is often found during a routine ultrasound test.
For those who do have symptoms, the most common is painless bleeding from the vagina during the second half of pregnancy. You also may have contractions. 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 everyone who has placenta previa has vaginal bleeding. In fact, about one-third of people with placenta previa don’t have this symptom.
How is placenta previa diagnosed?
A prenatal test that uses sound waves to show a picture of your baby in the womb (ultrasound) usually can find placenta previa and determine the placenta’s location. In some cases, your provider may do an ultrasound through the birth canal (transvaginal ultrasound) or a translabial ultrasound instead. In places where it’s available, three-dimensional ultrasound may be used.
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 requires repeat follow-up ultrasounds to assure that the cervix is no longer blocked. If the placenta is no longer covering the cervical opening, you can usually have a vaginal delivery.
How is placenta previa treated?
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. Your provider may recommend no vaginal exams or sex to prevent damage to the placenta and bleeding. Providers recommend c-section for nearly everyone with placenta previa to prevent severe bleeding.
If you are early in your pregnancy and have no symptoms, your provider will probably recommend no treatment, but will schedule follow-up ultrasounds to make sure everything is normal.
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 by having new blood put into your body (blood transfusions). Your provider also may give you medicines called corticosteroids to help speed up development of your baby’s lungs and other organs in case a preterm delivery is needed.
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 the lungs are fully developed. If they are, your provider may recommend an immediate c-section to avoid risks of future bleeding. Nowadays, providers may use corticosteroids to help the baby lung development while you are pregnant and to help avoid an immediate c-section.
At any stage of pregnancy, an emergency c-section may be necessary if you have dangerously heavy bleeding or if you and your baby are having problems.
Is there anything you should avoid if you have placenta previa?
If you have placenta previa that doesn’t require immediate treatment, your provider may recommend that you avoid doing the following:
- Having sex that leads to orgasm
- Vaginal penetration or vaginal examinations
- Moderate and strenuous exercise
- Lifting more than 20 pounds
- Standing for more than four hours
All of these activities could lead to contractions that could lead to bleeding.
How can you reduce your risk for complications if you have placenta previa?
Have an ultrasound in the second trimester to identify location of the placenta. You may need follow up ultrasounds to help plan for a safe birth and delivery.
Follow your providers precaution instructions to prevent bleeding or complications. Contact your provider and go to the hospital if you have bleeding at any time during your pregnancy.
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.
Last reviewed: January, 2022
Placenta previa occurs when the placenta covers the opening of the cervix during the last months of pregnancy. This condition can cause severe bleeding before or during labor.
The placenta develops in a pregnant person’s uterus during pregnancy. This sac-like organ provides the developing baby with food and oxygen. It also removes waste products from the baby’s blood. The placenta is also referred to as “afterbirth” because it exits the body after the baby is born.
During pregnancy, the uterus stretches and grows. It’s normal for the placenta to be low in the uterus in early pregnancy. As the pregnancy continues and the uterus stretches, the part of the uterine the placenta was stuck to moves, usually away from the cervical opening.
By the third trimester, the placenta should be near the top of the womb. This position allows the cervix, or the entrance to the womb at the bottom of the uterus, a clear path for delivery.
If the placenta attaches instead to the lower part of the uterus, it can cover part or all of the internal opening or “os” of the cervix. When the placenta covers the cervical os during the last months of pregnancy, the condition is known as placenta previa.
Most pregnant people with placenta previa will require pelvic rest. This typically includes abstaining from having sexual intercourse, limiting any procedures like an obstetrical check for dilation, and possibly restricting any exercises that may strain the pelvic floor.
The main symptom of placenta previa is sudden light to heavy bleeding from the vagina. Any bleeding can be representative of problems with the placenta and needs investigation by a physician. Specific symptoms may include:
- cramps or sharp pains
- bleeding that starts, stops, and begins again days or weeks later
- bleeding after intercourse
- bleeding during the second half of pregnancy
Risk factors for the development of placenta previa include:
- unusual position of the baby, including breech (buttocks first) or transverse (lying horizontally across the womb)
- previous surgeries that involve the uterus: cesarean delivery, surgery to remove uterine fibroids, dilation and curettage (D&C)
- pregnant with twins or other multiples
- prior miscarriage
- large placenta
- abnormally shaped uterus
- having already given birth to one child
- prior diagnosis of placenta previa
Pregnant people who are smokers, who are older than 35, or who are of Asian descent are also at higher risk of developing placenta previa.
Usually, the first signs of placenta previa will show up during the routine 20-week ultrasound. These initial signs are not necessarily a cause for worry, since the placenta is often lower in the uterus during the early part of a pregnancy.
The placenta usually corrects itself. According to the Royal College of Obstetricians and Gynaecologists, only 10 percent of people with low-lying placenta at 20 weeks will have a low-lying placenta at their next ultrasound. Only .5 percent will have placenta previa at the end of their pregnancy.
If you experience any bleeding in the second half of your pregnancy, doctors will monitor the position of the placenta using one of these preferred methods:
- Transvaginal ultrasound. Your doctor places a probe inside the vagina to provide an inside view of your vaginal canal and cervix. This is the preferred and most accurate method for determining placenta previa.
- Transabdominal ultrasound. A healthcare technician places gel on your abdomen and moves a handheld unit called a transducer around your abdomen to view the pelvic organs. The sound waves make a picture on a TV-like screen.
- MRI (magnetic resonance imaging). This imaging scan will help clearly determine the placenta’s location.
Doctors will decide how to treat your placenta previa based on:
- the amount of bleeding
- the month of your pregnancy
- the baby’s health
- the position of the placenta and the baby
The amount of bleeding is a doctor’s main consideration when deciding how to treat the condition.
Minimal to no bleeding
For cases of placenta previa with minimal or no bleeding, your doctor will likely suggest pelvic rest. This means refraining from putting anything into your vagina during pregnancy in order to prevent medical complications.
You’ll also be asked to avoid sex and likely exercise as well. If bleeding occurs during this time, you should seek medical care as soon as possible.
Heavy bleeding
In the case of heavy bleeding, your doctor will advise scheduling a cesarean delivery as soon as it’s safe to deliver — preferably after 36 weeks. If the C-section needs to be scheduled sooner, your baby may be given corticosteroid injections to speed up their lung growth.
Uncontrollable bleeding
In the case of uncontrolled bleeding, an emergency cesarean delivery will have to be performed.
During labor, the cervix will open to allow the baby to move into the vaginal canal for birth. If the placenta is in front of the cervix, it will begin to separate as the cervix opens, causing internal bleeding.
This can necessitate an emergency C-section, even if the baby is premature, as the pregnant person could bleed to death if no action is taken. Vaginal birth also poses too many risks for the pregnant person, who could experience severe hemorrhaging during labor, delivery, or after the first few hours of delivery.
A placenta previa diagnosis can be alarming for people who are expecting a baby. Here are some ideas for how to cope with your condition and how to prepare yourself for delivery.
Get educated. The more you know, the more you’ll know what to expect. Get in contact with other people who have been through placenta previa births.
Be prepared for your cesarean delivery. Depending on the type of your placenta previa, you might not be able to have a vaginal birth. It’s good to remember the ultimate goal — the health of you and your baby.
Rest. Pelvic rest is important while you are experiencing this condition. Additionally you should not engage in any strenuous activity or heavy lifting. You can use the time wisely by catching up on small projects, such as:
Pamper yourself. Indulge in small pleasures, such as:
- buying a new pair of comfortable pajamas
- reading a good book
- watching your favorite TV program
- keeping a gratitude journal
Be sure to rely on your circle of friends and family for conversation and support.