Placental abruption, or abruptio placentae, is a pregnancy complication in which the placenta peels away from the lining of the uterus prior to delivery.  Its severity depends on whether the separation is partial or complete. The abruption hampers the oxygen and nutrient supply to the baby,  sometimes causing heavy bleeding in the placenta and uterus.
It is most commonly classified depending on the nature of bleeding into two types:
Classification according to severity:
Placental abruption may or may not be painful and may even remain asymptomatic in rare cases. Apart from vaginal bleeding (in revealed abruption), classic signs include:
It is advisable to contact one’s health care provider immediately in case she experiences one or more of these symptoms.
The exact causes responsible for the abruption still remain unknown. Researches show a possible genetic association that increases the risk of an abruption. According to experts it may occur due to:
Prevention is not possible in most cases due to its unknown etiology. However, avoiding the risk factors, such as alcohol, smoking and cocaine, may reduce the chances of a placental abruption. According experts, women who follow a healthy diet and a proper exercise routine before conceiving are less at risk of developing an abruption. Those suffering from high blood pressure or diabetes during pregnancy should consult their health care provider to assess the risk factors. 
The diagnostician may perform a physical examination to determine the uterine rigidity or tenderness. Various diagnostic tests can be used for confirming the diagnosis.
It helps doctors to detect any intra-amniotic clotting, separation or rounding of placental edges and abnormal thickening of the placenta  which may indicate a placental abruption. However, an ultrasound test may not be enough to confirm the diagnosis.
Other diagnostic tests include:
The baby may have a mild jaundice after birth, which usually goes away automatically within a few days or weeks.
The treatment generally depends on the severity of the complication and stage of pregnancy in which it is diagnosed.
In case of mild or chronic abruption between the 24th and 34th week, the doctors may put the patients on bed rest to prevent further aggravation. Regular monitoring tests, like ultrasounds, are also performed to assess fetal growth. A small tear in the placenta may heal on its own without leading to any serious pregnancy complications.
If one develops a mild placental abruption at full term or during the later stages of the third trimester, the doctor may recommend a c-section birth or inducing labor.
A severe abruption may require immediate delivery of the baby to avoid further complications. Doctors often recommend a c-section birth.  Corticosteroid medications may be used to accelerate the development of the lungs and other organs of the baby in case of an emergency delivery. 
A blood transfusion  may be necessary in some rare cases where the mother suffers from heavy blood loss. Sometimes, it causes severe post-delivery hemorrhage which may call for an emergency hysterectomy (uterus removal) surgery. It helps with the management of the bleeding but also eliminates the possibility of conceiving ever again.
The outcome depends on the degree of placental separation from the uterus as well as the efficacy of the treatment. Severe placental abruption is associated with a considerable maternal and fetal mortality rate.
The chance of getting a placental abruption in a future pregnancy is 1 in 25, which increases to 1 in 5 in women with history of abruption in two earlier pregnancies.
It has been recorded in around 46,731 pregnancies with the incidence statistics being 6.2 in every 1,000 pregnancies. 
Its ICD-9 code is 641.2 while the ICD-10 code is O45.