What is Placenta Previa (Low-Lying Placenta)?

Placenta previa is when the placenta either partially or totally covers the cervix, which is the opening between the uterus and the vagina. Typically, the placenta attaches in the upper part of the uterus, and is what provides the baby with oxygen and nutrients and contributes to appropriate development. The placenta also helps to remove waste away from the baby. If the placenta is low-lying, it can cause severe bleeding during pregnancy and delivery. Women with placenta previa are also at an increased risk for premature birth.

During pregnancy or labor, if the woman has placenta previa, blood vessels that connect the placenta to the uterus may tear as the cervix opens. This can cause severe bleeding to happen. In most cases, women with placenta previa deliver through c-section.

Types

Types include:

• Partial. In this type, the cervix is only partially covered and there can still be a vaginal delivery.
• Marginal. The placenta begins to grow at the bottom of the uterus, but won’t cover the cervix. Due to the edge of the placenta touching the internal opening of the cervix, any overlap during delivery can cause bleeding. Discuss with your doctor if you can deliver vaginally.
• Complete. This is the most severe type of placenta previa. In this type, the placenta covers the entire cervix and the baby will have to be delivered through c-section and in the most severe cases, the baby may need to be delivered prematurely.

Symptoms

If any of the symptoms below occur, please consult with your healthcare provider immediately: 

• Vaginal bleeding after the 20th week of pregnancy, usually painless but you may have cramps or pain
• Sharp pains or cramps
• Bleeding after sex

Diagnosis

Typically, the first signs of placenta previa would present during a routine week 20 prenatal ultrasound scan. However, it is important to remember that it is actually normal for the placenta to sit lower in the uterus in the beginning of pregnancy. It is only cause for concern if the positioning of the placenta does not resolve on its own. Your healthcare provider will continue to monitor for bleeding in the second half of pregnancy and any changes in the placenta’s positioning.

There are different ways of diagnosing and monitoring placenta previa. Preferred methods include:

• Transvaginal ultrasound. This is the most accurate diagnostic tool for determining placenta previa. A doctor uses a probe inside the vagina to get a better look at the vaginal canal and cervix.
• Transabdominal ultrasound. A healthcare professional uses an ultrasound on the abdomen to view the pelvic organs. The soundwaves from the ultrasound create a picture on a screen for the doctor to assess.
• MRI (magnetic resonance imaging). The imaging scan will be able to determine the placenta’s exact location.

Causes

The specific cause of placenta previa is unknown.

Risk Factors

The development of placenta previa is more common in women who:

• Have had another baby
• Are pregnant with multiples
• Are older than 35
• Have scarring on the uterus
• Have had placenta previa before
• Are of a race other than white
• Smoke

Treatment

Your healthcare provider will determine the course of treatment, which is dependent upon the amount, frequency, and timing of any vaginal bleeding. Your doctor will also take into account the positioning of the placenta and the baby, as well as the baby’s health before determining a course of treatment. The main concern in determining treatment is the amount of bleeding. Treatments for placenta previa include:

• Minimal to no bleeding. A doctor will typically recommend bed rest, only standing or sitting when absolutely necessary. If bleeding happens during sex or exercise, it is important to contact your doctor immediately. Usually, it is recommended to avoid sex and exercise.
• Heavy bleeding. This may require a hospital stay and bed rest. It is possible that you may need a blood transfusion, depending on how much blood has been lost. Additionally, you may be given medication to prevent premature labor. A c-section is advised, but preferably not until after 36 weeks. If the c-section needs to happen sooner, a doctor may prescribe medication for the baby’s lungs to develop more quickly.
• Uncontrollable bleeding. If the bleeding is uncontrollable, an emergency c-section will have to be performed immediately.

Complications

A doctor will continue to monitor symptoms and changes with placenta previa. Complications may include:

• Bleeding. The vaginal bleeding can be severe enough to be life-threatening. Hemorrhaging can occur during labor, delivery, or within the first few hours after giving birth. 
• Preterm birth. Severe bleeding may require an emergency c-section before the baby is full term.