The placenta is an organ that provides oxygen and nutrition to a baby in the womb. It also removes wastes from the baby. Placenta previa is when this organ covers part or all of the cervix that the baby must pass through to be born.
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The cause is not known. It may be due to problems with how the placenta implants due to injury to the lining of the uterus and scarring from:
- Multiple prior pregnancies
- Prior placenta previa
- Prior cesarean delivery (C-section)
- Surgery to the lining of the uterus or to remove uterine fibroids
- Fertility treatments
Things that may raise the risk of this problem are:
- Prior cesarean delivery
- Prior abortion
- Being pregnant with a male fetus
- Smoking or cocaine use in the mother
Symptoms differ from person to person. It depends on how much of the cervix is covered. The main sign is painless bleeding from the birth canal. It can range from light to heavy. It most often happens after 20 weeks of pregnancy, usually after sex.
The doctor will ask about symptoms and health history. An ultrasound will be done. This can confirm the diagnosis.
The goal of treatment is to manage the bleeding and give the baby time to grow. How this is done will depend on the amount of bleeding a person has and how many weeks of pregnancy have passed. Options are:
- Monitoring the placenta for changes
- Pelvic rest—not having sex or using tampons
- Medicines to put off labor and give the fetus time to grow
A C-section will be needed to deliver the baby if the placenta covers the cervix, there is heavy bleeding during labor, or other health problems happen.
There are no known ways to prevent this health problem.
- Placenta previa. American Pregnancy Association website. Available at: https://americanpregnancy.org/healthy-pregnancy/pregnancy-complications/placenta-previa.
- Placenta previa. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/placenta-previa. Accessed May 9, 2022.
- Pregnancy complications. Office on Women's Health website. Available at: https://www.womenshealth.gov/pregnancy/youre-pregnant-now-what/pregnancy-complications.
- Beverly Siegal, MD, FACOG
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