Low-Lying Placenta (Placenta Previa)

Written by Shannon Johnson
Medically Reviewed by Jennifer Wider, MD

Placenta Previa

The placenta develops in a woman’s uterus during pregnancy. This sac-like structure 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,” for it exits the body after the baby is born.

During pregnancy, the placenta moves as the uterus stretches and grows. It is very normal for the placenta to be low in the uterus in early pregnancy. But as the pregnancy continues, the placenta typically moves to the top of the uterus. By the third trimester, the placenta should be near the top of the womb, so the cervix has a clear path for delivery. If the placenta attaches to the lower part of the uterus, it can cover part or all of the cervix (the entrance to the womb). When the placenta covers part or all of the cervix during the last months of pregnancy, this is a condition known as placenta previa, or low-lying placenta. This condition can cause severe bleeding before or during labor.

There are four types of placenta previa, ranging from minor to major (in which the placenta is covering the entire opening of the cervix). Depending on the type, a woman with placenta previa may need to have a Cesarean (C-section) delivery. Most women with this condition will require bed rest.

Symptoms Associated with Placenta Previa

The main symptom is sudden light to heavy bleeding from the vagina, but

if any of the symptoms below occur, you should seek immediate medical attention:

  • cramps
  • bleeding that starts, stops, and begins again days or weeks later
  • bleeding after intercourse
  • bleeding during the second half of pregnancy

Risk Factors for Developing Placenta Previa

Risk factors for the development of placenta previa include the following:

  • baby is in an unusual position: breech (buttocks first) or transverse (lying horizontally across the womb)
  • Previous surgeries that involve the uterus: C-section, surgery to remove uterine fibroids, Dilation and curettage (D&C)
  • pregnant with twins or other multiples
  • prior miscarriage
  • large placenta
  • abnormally shaped uterus
  • have already had one child
  • prior diagnosis of placenta previa
  • older than 35
  • Asian
  • smoker

How Is Placenta Previa Diagnosed?

Usually the first signs of placenta previa will show up during the routine 20-week ultrasound scan. 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 woman’s pregnancy.

The placenta usually corrects itself. In fact, only 10 percent of cases will go on to develop into full placenta previa (RCOG).

If you experience any bleeding in the second half of your pregnancy, doctors will monitor the position of the placenta using one of the following preferred methods:

  • transvaginal ultrasounds, in which the probe is placed 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
  • MRI (magnetic resource imaging), which will help to clearly determine the placenta’s location

Types of Placenta Previa

There are four types of placenta previa. Each will have its own effect on whether a mother can have a normal delivery or whether she will need a C-section. Treatment for placenta previa will also be based on which type you have.

Partial

The placenta only partially covers the opening of the cervix. Vaginal birth is still possible.

Low-Lying

This type begins in early to mid pregnancy. Placenta is positioned at the edge of the cervix, and there is a good chance you will be able to have a vaginal delivery.

Marginal

In this type, the placenta begins to grow at the bottom of the uterus. The placenta will normally push against the cervix but not cover it. Since the border of the placenta is touching the internal opening of the cervix, any overlap during labor could cause minor bleeding. However, vaginal births are normally safe.

Major or Complete

This is the most serious type. In this type, the placenta will eventually cover the entire cervix. C-sections are usually recommended, and in severe cases, the baby may have to be delivered prematurely.

With all types, heavy or uncontrollable bleeding may necessitate an emergency C-section to protect you and your baby.

Treatment of Placenta Previa

Doctors will decide how to treat your placenta previa based on the amount of bleeding, the month of your pregnancy, the baby’s health, and the position of the placenta and the baby. The amount of bleeding, however, is the main consideration when a doctor is making a decision on how to treat the condition.

Minimal to No Bleeding:

For cases of placenta previa with minimal or no bleeding, your doctor will likely suggest bed rest, which means resting in bed as much as possible—only standing and sitting when absolutely necessary. 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:

Cases of heavy bleeding may require hospital bed rest. Depending on the amount of blood lost, you may need blood transfusions. You may also need to take medicine to prevent premature labor.

In the case of heavy bleeding, your doctor will advise a C-section be scheduled as soon as it is 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 his or her lung growth.

Uncontrollable Bleeding

In the case of uncontrolled bleeding, an emergency C-section will have to be performed.

Complications of Placenta Previa

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 mother could bleed to death if no action is taken. Vaginal birth also poses too many risks for the mother, who could experience severe hemorrhaging during labor, delivery, or after the first few hours of delivery.

Coping and Support for Expectant Mothers

A placenta previa diagnosis can cast a pall over your pregnancy. The Mayo Clinic provides 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 will know what to expect. Get in contact with other women who have been through placenta previa births.
  • Be prepared for your C-section: Depending on the type of your placenta previa, you might not be able to have a vaginal birth. It is good to remember the ultimate goal—the health of you and your baby.
  • Enjoy bed rest: If you are active, bed rest can feel a bit confining. However, use the time wisely by catching up on small projects like putting together a photo album or writing letters, resting up, and reading about your upcoming lifestyle change.
  • Pamper yourself: Indulge in small pleasures. Buy a new pair of comfortable pajamas, read a good book, or watch your favorite TV program. Keep a gratitude journal. Rely on your circle of friends and family for conversation and support (Mayo).
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