Placental Abruption

What happens in placental abruption

The placenta attaches to the inner wall of the uterus and passes oxygen and nutrients from the mother's blood to the baby. In an abruption, blood vessels at the attachment site break, and bleeding pushes the placenta away from the wall.

Two things follow:

• The baby loses oxygen supply from the separated part of the placenta. Small separations are tolerated. Large ones can cause fetal distress or death within minutes.
• The mother loses blood, sometimes heavily. Blood may flow out through the vagina (revealed bleeding) or stay trapped behind the placenta (concealed bleeding). With concealed bleeding, the amount of visible blood greatly underestimates the real loss.

Grades of severity

Symptoms and signs of placental abruption

• Vaginal bleeding, often dark red. It can be light, heavy or absent.
• Abdominal pain, sudden and constant rather than coming and going. It may feel like a severe cramp.
• Back pain, especially if the placenta is on the back wall of the uterus.
• A hard, tender uterus that stays tense between contractions ("woody" uterus).
• Frequent, small contractions, sometimes one after another.
• Reduced baby movements.
• Signs of blood loss: dizziness, fast heart rate, pale clammy skin, fainting.

Symptoms can develop slowly over days (chronic abruption) with light intermittent bleeding and poor growth of the baby, but most abruptions are sudden.

Causes and risk factors

The exact trigger is often unknown. Known risk factors include:

• High blood pressure in pregnancy, including preeclampsia and chronic hypertension. This is the most common association.
• A previous abruption: the risk in the next pregnancy is about 10 times higher.
• Trauma to the belly: car crashes, falls and domestic violence. Abruption can follow even minor trauma, so monitoring is recommended after any significant blow.
• Smoking and cocaine or methamphetamine use, which narrow blood vessels.
• Waters breaking early (premature rupture of membranes), especially with infection.
• Rapid decompression of the uterus, such as delivery of a first twin or sudden loss of a large amount of amniotic fluid.
• Age over 35, carrying multiples, and blood clotting disorders.

How it is diagnosed

Placental abruption is primarily a clinical diagnosis, based on symptoms and examination. A clinician will check your blood pressure and pulse, examine your belly, and look at the amount of bleeding.

• Fetal heart monitoring (CTG) shows how the baby is coping and records contractions.
• Ultrasound confirms the baby's heartbeat and position and rules out placenta previa, where the placenta covers the cervix. It often cannot see an abruption, so a normal scan does not rule it out.
• Blood tests include a blood count, blood group and crossmatch, clotting tests and fibrinogen. A low fibrinogen suggests a severe abruption.
• Kleihauer test in Rh-negative women to measure how much fetal blood has entered the mother's circulation, to guide the anti-D dose.

Placental abruption vs placenta previa

Treatment

Treatment depends on how severe the abruption is, how far along the pregnancy is, and how mother and baby are coping.

• Severe abruption or a baby in distress: emergency delivery, usually by cesarean section, with blood transfusion and treatment of any clotting problems. If the baby has died and the mother is stable, vaginal birth may be safer.
• Mild abruption at or near term (37 weeks or more): delivery is usually recommended, often by inducing labor.
• Mild abruption before 34 weeks with a stable mother and baby: admission to hospital for close monitoring, steroid injections to mature the baby's lungs, and sometimes magnesium sulfate to protect the baby's brain if delivery before 32 weeks seems likely.
• Rh-negative mothers receive anti-D immunoglobulin.

Complications

For the mother:

• Heavy blood loss and shock
• Disseminated intravascular coagulation (DIC), where clotting factors are used up and bleeding becomes uncontrolled
• Kidney injury
• Need for blood transfusion and, rarely, hysterectomy

For the baby:

• Lack of oxygen and brain injury
• Premature birth and its complications (see preterm labor)
• Poor growth with chronic abruption
• Stillbirth in severe cases

Outlook and future pregnancies

With prompt treatment, most mothers recover fully. The outcome for the baby depends on how much of the placenta separated, how quickly delivery happened and how premature the baby is. After an abruption, a future pregnancy carries a higher risk of recurrence, so you will usually be offered closer monitoring, growth scans, blood pressure checks and planning for the timing of delivery.

Reducing the risk

• Attend all prenatal appointments and have your blood pressure checked.
• Stop smoking and avoid drugs, including cocaine.
• Wear a seatbelt correctly, with the lap belt below the bump and the shoulder strap between the breasts.
• Get checked after any fall or blow to the abdomen.
• Ask for help if you are being hurt at home. In the US, the National Domestic Violence Hotline is 1-800-799-7233.

Frequently asked questions

What are the first signs of placental abruption?

The first signs are often sudden belly or back pain, vaginal bleeding, and a uterus that feels hard and tender. Frequent contractions and fewer baby movements are other early signs. Bleeding can be hidden behind the placenta, so pain alone in later pregnancy needs urgent assessment.

What causes placental abruption?

The exact cause is often unknown. The strongest risk factors are high blood pressure and preeclampsia, a previous abruption, trauma to the belly, smoking and cocaine use. Early rupture of the membranes, carrying twins and being over 35 also raise the risk.

Can a baby survive placental abruption?

Yes, most babies survive, especially with mild abruptions and fast treatment. The outcome depends on how much of the placenta separated, how quickly the baby is delivered and how premature the baby is. Severe abruptions can cause brain injury or stillbirth.

Can placental abruption be seen on ultrasound?

Sometimes, but often not. Ultrasound detects only a minority of abruptions, because fresh blood can look like the placenta. A normal scan does not rule it out. Doctors rely mainly on symptoms, examination and fetal heart monitoring, and use ultrasound to rule out placenta previa.

Can you have a placental abruption without bleeding?

Yes. In a concealed abruption, the blood stays trapped between the placenta and the uterus wall, so there may be little or no visible bleeding. Pain, a hard uterus and changes in the baby's heart rate may be the only signs, which is why constant pain needs urgent assessment.