What is placenta abruptio?

Normally during pregnancy, the placenta is firmly attached to the inner wall of the uterus until the baby has been born. Placenta abruptio is the premature separation (abruption) of the placenta before childbirth. Since the round, flat placenta is a "lifeline" that supplies nutrients and oxygen to a fetus from the mother, an abruption can be life-threatening for the fetus, and sometimes for the mother as well. Placenta abruptio can lead to preterm birth, low birth weight [at or below 2500g], and major maternal blood loss. In rare cases, severe placenta abruptio leads to fetal or newborn death.¹

See a picture of placenta abruptio.

Placenta abruptio, also referred to as abruptio placenta or placental abruption, affects about 9 in 1,000 pregnancies.² It usually occurs in the third trimester of pregnancy, but it can occur any time after the 20th week. Up to 15 of every 100 abruptions aren't obvious until labor is in progress or after delivery.³

What causes placenta abruptio?

The causes of placenta abruptio are not well understood, and some women develop it without any identifiable cause. But you can reduce your risk by treating or avoiding some of the known risk factors that have been linked to placenta abruptio.

Common risk factors for placenta abruptio include:

• High blood pressure (140/90 mm Hg or higher), whether it is chronic or has been caused by the pregnancy (pregnancy-induced hypertension or preeclampsia). High blood pressure is the most common risk factor linked to placenta abruptio.
• A past placental abruption. If you have had more than one abruption, your risk is greater.
• Cigarette smoking. The more you smoke, the greater your risk of abruption. Up to 25 of every 100 placental abruptions are linked to cigarette smoking.⁴

Other risk factors for placenta abruptio include cocaine use; having a surgical scar or uterine fibroid where the placenta has attached; trauma to the uterus, as might occur in a car accident; and premature rupture of membranes for 24 hours or more, especially when there is an infection in the uterus.

What are the common symptoms?

If you have developed placenta abruptio, you may notice one or more symptoms, including:

• Vaginal bleeding that is light or heavy, dark or bright red, depending on the location of the abruption and how long it's taken for the blood to pass.
• A tender, painful, or hard, rigid-feeling uterus.
• Signs of preterm labor, including regular contractions, lower back or abdominal ache or pain.

The amount of vaginal bleeding isn't a good measure of how severe an abruption is-heavy bleeding is sometimes the least apparent because the blood can remain trapped between the placenta and uterine wall. Heavy blood loss can cause symptoms of shock, including lightheadedness, weakness, confusion, restlessness, and shallow, rapid breathing.

How is placenta abruptio diagnosed?