Abruptio Placentae 

Abruptio placentae is defined as the premature separation of the placenta from the uterus. Patients with abruptio placentae, also called placental abruption, typically present with bleeding, uterine contractions, and fetal distress. A significant cause of third-trimester bleeding associated with fetal and maternal morbidity and mortality, placental abruption must be considered whenever bleeding is encountered in the second half of pregnancy. Placental abruption is demonstrated in the image below. (See Clinical.)

Complications

Hemorrhage into the decidua basalis occurs as the placenta separates from the uterus. Vaginal bleeding usually follows, although the presence of a concealed hemorrhage in which the blood pools behind the placenta is possible. (See Workup.)

Hematoma formation further separates the placenta from the uterine wall, causing compression of these structures and compromise of blood supply to the fetus. Retroplacental blood may penetrate through the thickness of the uterine wall into the peritoneal cavity, a phenomenon known as Couvelaire uterus. The myometrium in this area becomes weakened and may rupture with increased intrauterine pressure during contractions. A myometrium rupture immediately leads to a life-threatening obstetric emergency. (See Treatment.)

Classification of placental abruption

Classification of placental abruption is based on extent of separation (ie, partial vs complete) and location of separation (ie, marginal vs central). (See Clinical.) Clinical classification is as follows:

• Class 0 - Asymptomatic
• Class 1 - Mild (represents approximately 48% of all cases)
• Class 2 - Moderate (represents approximately 27% of all cases)
• Class 3 - Severe (represents approximately 24% of all cases)

A diagnosis of class 0 is made retrospectively by finding an organized blood clot or a depressed area on a delivered placenta.

Class 1 characteristics include the following:

• No vaginal bleeding to mild vaginal bleeding
• Slightly tender uterus
• Normal maternal BP and heart rate
• No coagulopathy
• No fetal distress

Class 2 characteristics include the following:

• No vaginal bleeding to moderate vaginal bleeding
• Moderate to severe uterine tenderness with possible tetanic contractions
• Maternal tachycardia with orthostatic changes in BP and heart rate
• Fetal distress
• Hypofibrinogenemia (ie, 50-250 mg/dL)

Class 3 characteristics include the following:

• No vaginal bleeding to heavy vaginal bleeding
• Very painful tetanic uterus
• Maternal shock
• Hypofibrinogenemia (ie, < 150 mg/dL)
• Coagulopathy
• Fetal death

Go to Emergent Management of Abruptio Placentae for complete information on this topic.

The primary cause of placental abruption is usually unknown, but multiple risk factors have been identified.^{[1, 2]} However, only a few events have been closely linked to this condition.

Risk factors in abruptio placentae include the following:

• Maternal hypertension - Most common cause of abruption, occurring in approximately 44% of all cases
• Maternal trauma (eg, motor vehicle collision [MVC], assaults, falls) - Causes 1.5-9.4% of all cases
• Cigarette smoking
• Alcohol consumption
• Cocaine use
• Short umbilical cord
• Sudden decompression of the uterus (eg, premature rupture of membranes, delivery of first twin)
• Retroplacental fibromyoma
• Retroplacental bleeding from needle puncture (ie, postamniocentesis)
• Idiopathic (probable abnormalities of uterine blood vessels and decidua)^[3]
• Previous placental abruption
• Chorioamnionitis^[4]
• Prolonged rupture of membranes (24 h or longer)
• Maternal age 35 years or older
• Maternal age younger than 20 years
• Male fetal sex
• Low socioeconomic status
• Elevated second trimester maternal serum alpha-fetoprotein (associated with up to a 10-fold increased risk of abruption)
• Subchorionic hematoma^[5]

Cigarette smoking/tobacco abuse

Cigarette smoking increases a patient's overall risk of placental abruption.^[6]

A prospective cohort study showed the risk of abruption to be increased by 40% for each year of smoking prior to pregnancy.

In addition to the increased risk of abruption caused by tobacco abuse, the perinatal mortality rate of infants born to women who smoke and have an abruption is increased.^{[7, 8]}

Cocaine (powder or crack) abuse

The hypertension and increased levels of catecholamines caused by cocaine abuse are thought to be responsible for a vasospasm in the uterine blood vessels that causes placental separation and abruption. However, this hypothesis has not been definitively proven.

The rate of abruption in patients who abuse cocaine has been reported to be approximately 13-35% and may be dose-dependent.^[9]

Trauma

Abdominal trauma is a major risk factor for placental abruption.

Motor vehicle accidents often cause abdominal trauma. The lower seat belt should extend across the pelvis, not across the midabdomen, where the fetus is located.

Trauma may also be due to domestic abuse or assault, both of which are underreported.

Thrombophilia

While it was previously thought that patients who experienced early or severe abruptions were at increased risk of having a specific thrombophilia, this is no longer thought to be the case and screening of patients with an abruption is no longer recommended.

Frequency

United States

The frequency of abruptio placentae in the United States is approximately 1%, and a severe abruption leading to fetal death occurs in 0.12% of pregnancies (1:830).

The frequency of abruptio placentae in the United States is approximately 1%, and a severe abruption leading to fetal death occurs in 0.12% of pregnancies (1:830).

Abruptio placentae also occurs in about 1% of all pregnancies throughout the world.

Race predilection

Placental abruption is more common in African American women than in white or Latin American women. However, whether this is the result of socioeconomic, genetic, or combined factors remains unclear.

Age predilection

An increased risk of placental abruption has been demonstrated in patients younger than 20 years and those older than 35 years.

If the bleeding continues, fetal and maternal distress may develop. Fetal and maternal death may occur if appropriate interventions are not undertaken.

The severity of fetal distress correlates with the degree of placental separation. In near-complete or complete abruption, fetal death is inevitable unless an immediate cesarian delivery is performed.^[10]

If an abruption occurs, the risk of perinatal mortality is reported as 119 per 1,000 people in the United States, but this can depend on the extent of the abruption and the gestational age of the fetus.^[11] This rate is higher in patients with a significant smoking history.

Currently, placental abruption is responsible for approximately 6% of maternal deaths.

Morbidity associated with abruptio placentae

Fetal morbidity is caused by the insult of the abruption itself and by issues related to prematurity when early delivery is required to alleviate maternal or fetal distress.

Maternal morbidity may include the following:

• Transfusion-related morbidity
• Classic cesarean delivery with need for repeat cesarean deliveries
• Hysterectomy^[12]

Maternal and fetal complications include issues related to (1) cesarean delivery, (2) hemorrhage/coagulopathy, and (3) prematurity.

Cesarean delivery

Cesarean delivery is often necessary if the patient is far from her delivery date or if significant fetal compromise develops. If significant placental separation is present, the fetal heart rate tracing typically shows evidence of fetal decelerations and even persistent fetal bradycardia.

A cesarean delivery may be complicated by infection, additional hemorrhage, the need for transfusion of blood products, injury of the maternal bowel or bladder, and/or hysterectomy for uncontrollable hemorrhage. In rare cases, death occurs.

Hemorrhage/coagulopathy

Disseminated intravascular coagulation (DIC) may occur as a sequela of placental abruption. Patients with a placental abruption are at higher risk of developing a coagulopathic state than those with placenta previa. The coagulopathy must be corrected to ensure adequate hemostasis in the case of a cesarean delivery.

Prematurity

Delivery is required in cases of severe abruption or when significant fetal or maternal distress occurs, even in the setting of profound prematurity. In some cases, immediate delivery is the only option, even before the administration of corticosteroid therapy in these premature infants. All other problems and complications associated with a premature infant are also possible.

Recurrence

The risk of recurrence of abruptio placentae is reportedly 4-12%. If the patient has abruptio placentae in 2 consecutive pregnancies, the risk of recurrence rises to 25%.

If the abruption is severe and results in the death of the fetus, the risk of a recurrent abruption and fetal demise is 7%.

Educate patients about reversible risk factors, especially smoking, before further pregnancies.

Question the patient regarding possible trauma from abuse.