A placental abruption is a serious potentially life threatening condition.
In a normal pregnancy the placenta is attached to the uterine wall however for some women, roughly 1 out of 200 pregnancies the placenta partially or completely detaches from the uterine wall.
This condition is most common during the last stage of pregnancy, the third trimester.
When the placenta separates from the uterine wall many things can happen.
First and foremost is the possibility of severe bleeding which can be life threatening to both mother and baby.
A partial abruption can deprive the baby of oxygen and nutrients needed for healthy development.
This increases the risks of intrauterine growth restriction, premature delivery, and stillbirth.
There are factors that increase your risk of developing placental abruption.
These include but are not limited to:

• Getting pregnant after the age of 35
• Having more than 4 children
• Being pregnant with multiples (even twins)
• Having high blood pressure (even pregnancy induced hypertension)
• Use of cocaine
• Use of tobacco
• Diabetes (even gestational)
• A previous abruption

Placental abruption often has no symptoms.
However symptoms can include:

• Constant contractions
• Pain in the uterus or back
• Vaginal bleeding

Treatment of placental abruption varies and will depend on many factors.
All of the following will be considered (there may be more that your doctor considers).

• Baby's health
• How much of the placenta is separated
• Amount of blood loss
• And other health issues you may have
• How far along you are in your pregnancy

The best case scenario is that it is a very small separation with no fetal distress in which case you may be allowed to remain at home.
If there is fetal distress or the separation is great then your doctor may want to admit you for observation or immediate delivery.
The delivery will likely be by cesarean section.