Placenta Previa: Root Causes, Symptoms, and Treatments

Updated 03 June 2020

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Reviewed by Olga Adereyko, MD, Primary Care Physician, General Practitioner, Medical Consultant

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Placenta previa is a condition in which the placenta at least partially obstructs your cervix, creating labor and delivery complications. Keep reading to learn the contributing factors for placenta previa as well as key implications it may have on your pregnancy.

What is placenta previa?

The placenta serves as the link between mother and baby during pregnancy. It’s a structure in your uterus, connected by an umbilical cord, that transfers oxygen and nutrients to your child. Ordinarily, the placenta attaches to the top or side of your uterus and gets expelled after delivery.

So “what is placenta previa?” It’s when the placenta positions itself at the bottom of your uterus, partially or completely covering your cervix (i.e., the bridge between your vagina and uterus). 

During childbirth, the placenta previa condition might cause severe bleeding, putting both your health and your baby’s in jeopardy. Since uterine growth speeds up after week 20, your placenta could shift, either away from or toward your cervix. The latter is more likely if you happen to have a low placenta. 

Furthermore, bleeding triggered by a low-lying placenta isn’t just confined to the delivery room. A low placenta has also been known to cause bleeding throughout pregnancy. If you notice any bleeding or spotting, please consult your obstetrician right away. Avoid activities that could disrupt the placenta or set off contractions, such as vigorous exercise, tampon use, douching, sex, or even jumping and squatting.

The presence of placenta previa generally means your child will be delivered via C-section, should the problem fail to resolve itself. In some cases, though, as your uterus continues to expand, the placenta may gradually move away from your cervix.

Types of placenta previa

There are two different types of placenta previa: complete placenta previa and marginal placenta previa. With the former, your entire cervix is covered; whereas, a marginal placenta previa means it’s less than two centimeters from the internal opening.

The diagnosis of placenta previa involves an ultrasound examination (around week 20) to pinpoint the placenta’s exact location. Follow-up care entails close monitoring of its movement as your pregnancy progresses. 

Placenta previa symptoms

The most common of placenta previa symptoms is the appearance of bright red blood, not accompanied by pain. This typically happens in the latter half of your pregnancy, occasionally in conjunction with contractions. Since the placenta carries a high concentration of blood vessels, cervical expansion during childbirth or even mild contractions (e.g., Braxton-Hicks) could result in bleeding.

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The most common of placenta previa symptoms is the appearance of bright red blood, not accompanied by pain.

Fortunately, some pregnant women are diagnosed with placenta previa early on, when the problem is more likely to resolve on its own. 

If, at any point, you notice vaginal bleeding while pregnant, please seek medical attention immediately.

Causes of placenta previa

The exact reason for placenta previa is still unknown, but certain factors can raise your likelihood of developing it. If you experienced placenta previa in previous pregnancies or if you sustained uterine scars from a C-section, the placenta may not implant itself properly. And a low placenta is particularly prone to blocking your cervix as pregnancy progresses. 

The same can be said of larger placentas. Depending on your little one’s unique needs, the placenta could be a bit on the smaller or larger side. It’s designed to expand accordingly to provide the right amount of nutrients and oxygen for multiple babies, for instance. 

A few other things should be taken into account with regard to placenta size:

• Pregnant women who smoke typically grow larger placentas (note that tobacco use also encourages low birth weight, early delivery, and newborn lung issues).
• Living in higher altitudes is potentially linked to placenta previa and a larger-than-average placenta. Though moving away may be out of the question, your doctor will want to monitor you more closely.

Other contributing factors for placenta previa

There are a number of other circumstances affecting your likelihood of experiencing placenta previa which include:

• Having prior pregnancies (especially if placenta previa occurred before)
• Uterine damage (e.g., C-section scarring, surgical fibroid removal, or dilation and scraping of the uterus after a miscarriage)
• Carrying multiple fetuses (e.g., twins, triplets, etc.)
• Advanced age (if you’re over 35)
• Tobacco and drug use 
• Being overweight or obese 

Lastly, placenta previa seems particularly prevalent among non-Caucasian races, such as in Asian women.

Ways to treat placenta previa

Although placenta previa isn’t curable, it is treatable. Management of the placenta previa condition includes controlling the bleeding and alleviating stress on your cervix and uterus. Whether or not management is effective directly depends on: 

• The state of your current health and your baby’s
• The severity of bleeding and if it stops on its own
• How far along you are in the pregnancy 
• The fetal position 

Unfortunately, surgery and medications are not viable options for placenta previa. If bleeding is heavy, hospitalization may be required; however, if bleeding is light or resembles spotting, your doctor might simply recommend bed rest and limiting activity.

If you’re still not experiencing any relief from placenta previa, the goal will be to get you as close as possible to full term. Expect to have a C-section delivery, as a vaginal delivery could lead to excessive bleeding or cause a placental rupture.

Possible complications of placenta previa

Placenta previa may result in severe vaginal bleeding, or hemorrhaging, throughout pregnancy, especially if you start to feel contractions. Hemorrhaging may even continue during labor and in the hours following childbirth. 

Your doctor should also closely monitor your placental movement to prevent complications such as early or preterm delivery to keep you and your baby safe.

Takeaway

Placenta previa is a pregnancy-related condition with potentially serious consequences for you and your unborn child. Treatment of placenta previa primarily involves careful observation and management of bleeding. If your case of placenta previa does not resolve itself and you notice heavy bleeding, seek emergency medical care right away.

History of updates

Current version (03 June 2020)

Reviewed by Olga Adereyko, MD, Primary Care Physician, General Practitioner, Medical Consultant

Published (03 June 2020)