Description

Bleeding at the decidua-placental interface. The diagnosis is typically reserved for pregnancies after 20 weeks.

Epidemiology

Incidence

• The overall prevalence rate of abruption in United States is 9.6/1,000, of which 2/3 of cases were classified as being severe (6.5/1,000).
• 80% of cases occur prior to onset of delivery.
• 40–60% occur before 37 weeks of gestation; 14% occur before 32 weeks.
• Risk of placental abruption is higher if:
  • History placental abruption in first pregnancy
  • Hypertensive disorders in the index pregnancy
  • At extremes of age in the reproductive window

Etiology and Pathophysiology

• Acute
  • Etiology of bleeding at the decidua basalis in most cases remains elusive.
  • May be caused by sudden mechanical events, such as blunt abdominal trauma or rapid uterine decompression when rupture of gestational membranes occurs, especially with polyhydramnios
  • Acute hypertension due to vasospasm or secondary to cocaine use
  • Uterine abnormalities: bicornuate uterus, uterine synechiae, leiomyomas, prior hysterotomy
• Chronic (majority of cases)
  • Occurs in chronic hypertensive disorders and associated with fetal growth restriction
  • Early bleeding in pregnancy releases thrombin and initiates chronic inflammatory pathophysiology.
  • Smoking
• Abruption is a shared final clinical outcome of diverse clinical pathways.

Genetics

• In context of the condition’s multifactorial etiology, a genetic etiology is possible for some cases. Larger case-control studies that include gene–gene and gene–environment interactions may elucidate the genetics of placental abruption.
• Placental growth is primarily under control of paternally inherited fetal genes.

Risk Factors

• Prior placental abruption increases risk by 15- to 20-fold.
• Increasing maternal age and parity
• Maternal smoking habit: dose–response relationship
• Cocaine use and abuse
• Hypertensive disorders (chronic hypertension, preeclampsia, eclampsia)
• Uterine anomalies
• Multiple-gestation pregnancies
• 1st- or 2nd-trimester bleeding
• Preterm rupture of membranes
• Polyhydramnios
• Severe small-for-gestational-age birth
• Blunt trauma/motor vehicle accident
• Chorioamnionitis
• Male infant

General Prevention

Behavioral modifications to ameliorate abruption risk:

• Smoking cessation
• Cease cocaine abuse.
• Use seat belts.

Commonly Associated Conditions

• Prenatal risks
  • Preeclampsia and other forms of hypertension in pregnancy
  • Uteroplacental insufficiency
  • Rupture of membranes
• Postnatal risks
  • Postpartum hemorrhage
  • Disseminated intravascular coagulation (DIC)
  • Maternal anemia