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Placenta Previa & Pregnancy: Can It Cause Miscarriage?
Causes, symptoms and treatment of placenta previa in pregnancy
Bleeding during pregnancy is a frightening experience that can elicit worry and panic in an expectant mother. Fortunately, not all bleeding indicates a major problem or poses an immediate risk to a baby’s health.
Light, painless bleeding during the 2nd and 3rd trimesters of pregnancy may be the result of a condition known as placenta previa, which affects about 1 in 200 pregnancies in the U.S. each year.
If you experience bleeding, with or without pain, at any time during your pregnancy, it’s important to contact an experienced OB-GYN immediately.
What is placenta previa?
To understand placenta previa, it’s necessary to know how the placenta functions in a healthy pregnancy.
The placenta is a temporary organ that develops on the wall of a woman’s uterus during pregnancy. It provides the growing baby with essential oxygen and nutrients while in the womb. These nutrients are delivered to the baby through the umbilical cord, which connects the baby and the placenta.
Normally, the placenta attaches to the top or side of the uterine wall. In placenta previa, however, the placenta attaches to the cervix, which is located at the base of the mother’s uterus.
Because the baby needs to pass through the cervix for a vaginal delivery to occur, placenta previa can result in various pregnancy complications and may require a cesarean delivery (C-section).
Types of placenta previa
Placenta previa can be divided into 3 categories. Which type you have depends on how much of your cervix is covered by your placenta.
- Complete placenta previa occurs when the placenta covers the entire cervix.
- Partial placenta previa occurs when the placenta partially covers the cervix.
- Marginal placenta previa occurs when the placenta is at the edge (margins) of the cervix.
The more your placenta covers your cervix, the more likely you are to experience symptoms and complications from placenta previa.
What are the symptoms of placenta previa?
The most common symptom of placenta previa is bright red vaginal bleeding during the 2nd and 3rd trimesters of pregnancy that is not accompanied by pain. Some women also experience mild contractions.
Risk factors for placenta previa
The cause of placenta previa is still unknown, but women are more likely to experience placenta previa during their pregnancy if they:
- Have scars on their uterus from a prior surgery such as a C-section or dilation and curettage (D&C)
- Have uterine fibroids (noncancerous tumors in the uterus)
- Are carrying more than 1 baby
- Are over the age of 35
- Are non-white
- Smoke cigarettes
- Use cocaine
- Had placenta previa in a previous pregnancy
- Are pregnant with a boy
How is placenta previa diagnosed?
In order to diagnose placenta previa, your doctor will need to ask you questions about your health history, do a physical exam and perform an ultrasound. The ultrasound will show where your placenta is located and how much of your cervix is covered by your placenta. If placenta previa is seen on ultrasound, your doctor will likely order additional ultrasounds to monitor the location of your placenta as your pregnancy progresses.
If your initial ultrasound shows that you have placenta previa, there’s no reason to panic. Most of the time, placenta previa resolves on its own before the baby is born. In fact, in one study of more than 1,400 women, 98.4 percent of placenta previa cases diagnosed during the 2nd trimester resolved before the end of pregnancy.
Because a woman’s uterus enlarges throughout pregnancy to accommodate her ever-growing baby, her placenta often pulls away from her cervix as her uterus expands. Women diagnosed with partial or marginal placenta previa have a greater chance of their placenta moving completely off of their cervix before delivery than those diagnosed with complete placenta previa.
Complications of placenta previa
The biggest risk with placenta previa is severe bleeding, also known as hemorrhage. This is most likely to occur toward the end of pregnancy as the uterus begins thinning out in preparation for childbirth. The more the cervix is covered by the placenta, the greater the risk of bleeding.
Other potential complications of placenta previa include:
- Intrauterine growth restriction (IUGR) or delayed fetal growth from inadequate blood supply
- Preterm birth (before 37 weeks)
- Heath issues for the baby (due to an early birth)
- Stillbirth
- Maternal shock (from excessive blood loss)
Is there a treatment for placenta previa?
There is no cure for placenta previa, but your doctor will monitor your symptoms to make sure you and your baby remain healthy and safe. If your doctor has any concerns, they may recommend:
- Abstaining from activities that can cause uterine contractions (such as sexual intercourse)
- Maternal blood transfusions (for anemia/blood loss)
- Close monitoring of mother and baby (possibly in a hospital setting)
- Early delivery
Because complete placenta previa blocks the opening for a baby to be born vaginally, women whose placenta previa doesn’t resolve before the end of their pregnancy will need to have a C-section to deliver their baby safely.
What should I do if I experience bleeding during pregnancy?
If you experience bleeding at any time during your pregnancy, it’s vital that you contact a qualified OB-GYN right away so they can assess you and your baby and determine a cause. Although a small amount of painless bleeding often isn’t a cause for concern, your doctor will monitor your symptoms and recommend appropriate treatment based on your individual situation.