# Placental Abruption and Antepartum Hemorrhage

## Placental Abruption

### Definition

Placental abruption is the premature separation of a normally implanted placenta from the uterine wall before delivery, occurring after 20 weeks' gestation. It complicates 0.5 to 1% of pregnancies and is a significant cause of both maternal and perinatal morbidity and mortality.

### Pathophysiology

Abruption begins with rupture of the maternal decidual spiral arteries, which leads to bleeding at the decidual-placental interface. A retroplacental hematoma forms and progressively separates the placenta from the uterine wall, disrupting the transfer of oxygen and nutrients to the fetus. The release of thromboplastin from the damaged decidua can trigger disseminated intravascular coagulation (DIC). In concealed hemorrhage, blood becomes trapped behind the placenta with no external vaginal bleeding, which means the visible blood loss can vastly underestimate the true hemorrhage.

### Risk Factors

The strongest risk factor for abruption is a prior abruption, which confers a recurrence risk of 5 to 17%. Other significant risk factors include chronic hypertension and preeclampsia, trauma (motor vehicle accidents, domestic violence, falls), cocaine and methamphetamine use, cigarette smoking, PPROM (especially with oligohydramnios), thrombophilias (factor V Leiden, prothrombin gene mutation), uterine anomalies and fibroids (particularly retroplacental fibroids), polyhydramnios (with rapid decompression), short umbilical cord, and advanced maternal age with multiparity.

### Classification by Severity

Grade 1 (mild) abruption, accounting for approximately 40% of cases, involves a small retroplacental clot with minimal or no vaginal bleeding, no fetal distress, and stable maternal hemodynamics. Grade 2 (moderate) abruption, approximately 45% of cases, presents with moderate vaginal bleeding, uterine tenderness and tetany, fetal distress (decelerations, tachycardia), and possible mild coagulopathy. Grade 3 (severe) abruption, approximately 15% of cases, involves massive hemorrhage, profound fetal distress or demise, DIC, hemodynamic instability, and a board-like rigid uterus. Grade 3 is further subdivided into 3A (without coagulopathy) and 3B (with coagulopathy).

| Grade | Frequency | Bleeding | Uterus | Fetal Status | Coagulopathy |
|---|---|---|---|---|---|
| 1 (Mild) | ~40% | Minimal or none | Mildly tender | Reassuring | None |
| 2 (Moderate) | ~45% | Moderate | Tender, tetanic | Distressed | Possible (mild) |
| 3A (Severe) | ~15% | Massive | Board-like, rigid | Demise common | No |
| 3B (Severe) | — | Massive | Board-like, rigid | Demise common | Yes (DIC) |

### Clinical Presentation

Vaginal bleeding is present in approximately 80% of cases but may be entirely absent in concealed abruption. The hallmark findings are abdominal pain and uterine tenderness, often accompanied by uterine hypertonicity or high-frequency contractions. Back pain may indicate a posterior placental location. Fetal heart rate abnormalities including late decelerations, bradycardia, and sinusoidal pattern reflect fetal compromise. Maternal tachycardia and hypotension develop in severe cases. Port-wine colored amniotic fluid may be noted.

### Diagnosis

Placental abruption is a clinical diagnosis, and management should not be delayed to obtain imaging. Ultrasound has a sensitivity of only 25 to 50% for detecting abruption because the retroplacental hematoma may be isoechoic with the placenta, particularly when acute. The absence of ultrasound findings does not exclude abruption. Ultrasound remains useful for ruling out placenta previa and assessing fetal viability. Laboratory evaluation includes CBC, coagulation panel (PT, PTT, fibrinogen), type and crossmatch, and Kleihauer-Betke test. A fibrinogen level below 200 mg/dL is critically abnormal in pregnancy (where normal values range from 350 to 600 mg/dL) and suggests DIC.

<image>Diagram showing three types of placental abruption: revealed abruption with vaginal bleeding, concealed abruption with retroplacental hematoma but no external bleeding, and mixed type with both retroplacental collection and vaginal bleeding</image>

### Management

#### Mild Abruption (Grade 1), Preterm, Stable

Management includes hospitalization with continuous fetal monitoring, serial hemoglobin and coagulation studies, IV access with type and crossmatch, and antenatal corticosteroids if the gestational age is below 34 weeks. If both maternal and fetal status remain reassuring, expectant management can continue, with consideration for discharge after 48 to 72 hours of stability for close outpatient follow-up. If expectant management continues without incident, delivery is planned at 37 weeks.

#### Moderate-Severe Abruption (Grade 2-3)

Immediate management follows ABCs: two large-bore IV lines (16 to 18 gauge) are established and aggressive fluid resuscitation is initiated. The massive transfusion protocol is activated for significant hemorrhage, targeting a 1:1:1 ratio of packed red blood cells to fresh frozen plasma to platelets. Fibrinogen is replaced with cryoprecipitate if levels fall below 200 mg/dL. Continuous fetal monitoring guides delivery decisions. If the fetus is viable with a non-reassuring tracing, emergent cesarean delivery is performed. In the case of fetal demise, vaginal delivery is preferred because it avoids adding surgical morbidity to an already coagulopathic patient. Amniotomy may be performed to accelerate labor and reduce thromboplastin release. The team should prepare for postpartum hemorrhage, as uterine atony is common after abruption, particularly in the setting of Couvelaire uterus (where blood has infiltrated the myometrium, impairing its ability to contract).

#### DIC Management

Cryoprecipitate (10 units, which raises fibrinogen by approximately 70 mg/dL) is given for fibrinogen below 100 mg/dL. Platelets are transfused if the count falls below 50,000, and FFP is given for prolonged PT/PTT. Delivery is the definitive treatment for abruption-related DIC.

## Differential Diagnosis of Third-Trimester Bleeding

The three major causes of significant third-trimester bleeding have distinguishing features. Abruption typically presents with dark red bleeding that may be concealed, abdominal pain with uterine tenderness, a hypertonic and tender uterus, and often compromised fetal status. Placenta previa presents with bright red, painless bleeding, a soft and nontender uterus, and a usually reassuring fetal heart rate tracing. Vasa previa presents with bleeding associated with rupture of membranes, an absence of pain, normal uterine tone, and rapid fetal distress or demise. Other causes of antepartum hemorrhage include cervical pathology (polyps, cervicitis, cancer), bloody show or labor, uterine rupture (especially during VBAC), trauma, genital lacerations, and coagulopathy.

| Feature | Abruption | Placenta Previa | Vasa Previa |
|---|---|---|---|
| Bleeding color | Dark red (may be concealed) | Bright red | Associated with ROM |
| Pain | Significant; uterine tenderness | Painless | None |
| Uterine tone | Hypertonic, rigid | Soft, nontender | Normal |
| Fetal status | Often compromised | Usually reassuring | Rapid distress/demise |
| Onset trigger | Spontaneous or trauma | Spontaneous | ROM or amniotomy |

## Approach to Antepartum Hemorrhage

### Initial Assessment

The initial approach follows a systematic sequence: ABCs and hemodynamic stabilization, determination of gestational age, establishment of two large-bore IVs with type and crossmatch, continuous fetal monitoring, and -- critically -- no digital cervical examination until placenta previa has been excluded by ultrasound. A speculum exam can be performed to evaluate the cervix for lesions, dilation, and bleeding source. Ultrasound assesses placental location, fetal viability, and amniotic fluid volume. Laboratory evaluation includes CBC, coagulation panel, fibrinogen, type and screen/crossmatch, and Kleihauer-Betke test.

### RhoGAM

All Rh-negative patients with antepartum hemorrhage should receive anti-D immunoglobulin (RhoGAM). The Kleihauer-Betke test quantifies fetomaternal hemorrhage and determines whether additional doses are needed beyond the standard 300 mcg.

<image>Clinical algorithm flowchart for the evaluation and management of antepartum hemorrhage, starting with maternal stabilization, followed by ultrasound to rule out previa, then branching into management pathways for abruption, previa, vasa previa, and other causes based on clinical findings</image>

## Complications of Abruption

### Maternal

Maternal complications include hemorrhagic shock, DIC (occurring in 10 to 20% of severe abruptions), renal failure from acute tubular necrosis, Couvelaire uterus (blood infiltration of the myometrium that impairs uterine contraction and may not respond to uterotonics), the need for hysterectomy, and, rarely in developed countries, maternal death (less than 1%).

### Fetal/Neonatal

Fetal and neonatal complications include fetal distress and death (perinatal mortality of 10 to 30% in severe abruption), preterm delivery, growth restriction from chronic partial abruption, and neonatal anemia.

## Recurrence and Prevention

The recurrence risk after one prior abruption is 5 to 17%, increasing to as high as 25% after two prior episodes. There is no proven prevention strategy, but modifiable risk reduction includes smoking cessation, treatment of hypertension, and avoidance of cocaine and stimulants. Low-dose aspirin given for preeclampsia prevention may indirectly reduce abruption risk. Close surveillance in subsequent pregnancies includes serial growth ultrasound and antenatal testing from 32 weeks.

## Clinical Pearls

Abruption is a clinical diagnosis. A normal ultrasound does not exclude it, and management should never be delayed while awaiting imaging.

Concealed abruption may present with pain and fetal distress but minimal or no vaginal bleeding. The degree of visible hemorrhage does not reflect the true blood loss.

Fibrinogen is the earliest and most sensitive laboratory marker of DIC in abruption. A level below 200 mg/dL in pregnancy is critically abnormal and should trigger immediate replacement.

In fetal demise from abruption, vaginal delivery is preferred because cesarean delivery adds surgical morbidity to an already coagulopathic patient.

Always exclude placenta previa with ultrasound before performing a digital cervical exam in any patient with antepartum hemorrhage.

Couvelaire uterus does not necessarily require hysterectomy. Uterotonics, compression sutures, and intrauterine balloon tamponade should be attempted first.

Trauma is a preventable cause of abruption. Screening for domestic violence and counseling on proper seatbelt use are important components of prenatal care.

## References

- ACOG Practice Bulletin No. 227: Placental Abruption (2021)
- Oyelese Y, Ananth CV. Placental abruption. Obstet Gynecol. 2006;107:1005-1016
- Ananth CV, Lavery JA, Vintzileos AM. Fetal Growth Restriction and Preeclampsia: Risk Factor Profiles and Placental Lesions. Am J Perinatol. 2015
- Tikkanen M. Placental abruption: epidemiology, risk factors, and consequences. Acta Obstet Gynecol Scand. 2011;90:140-149
- SMFM Consult Series: Management of Bleeding in Late Pregnancy. Am J Obstet Gynecol. 2020