What causes placental abruption?

What Causes Placental Abruption

Placental abruption results from rupture of maternal decidual arteries causing dissection at the decidual-placental interface, driven by both chronic processes (decidual and uteroplacental vasculopathy, impaired placentation) and acute processes (shearing forces from trauma, acute vasospasm, or sudden hypertensive events). 1, 2

Primary Pathophysiologic Mechanisms

The underlying pathophysiology involves overlapping processes that lead to premature placental separation:

• Vascular pathology: Defective trophoblastic invasion of spiral arteries and subsequent abnormal early vascularization create a vulnerable vascular bed 2
• Decidual arteriopathy: Rupture of maternal decidual arteries at the decidual-placental interface is the final common pathway 2
• Acute vasospasm: Small vessel vasospasm may precede the actual separation 2
• Inflammatory processes: Systemic or local inflammation affecting the vascular bed contributes to vessel fragility 2
• Uteroplacental underperfusion: Chronic placental insufficiency and intrauterine hypoxia weaken placental attachment 2

Major Risk Factors and Their Associations

Strongest Risk Factors (Highest Odds Ratios)

• Cocaine use: Pooled OR 3.92 (95% CI 2.77-5.46) through massive sympathomimetic effects causing acute vasoconstriction and hypertensive crises 3
• Prior placental abruption: Most significant historical risk factor 4
• Trauma: Direct shearing forces applied to the abdomen cause acute separation 1

Hypertensive Disorders

• Preeclampsia and chronic hypertension: Create decidual vasculopathy and increase acute vascular stress 4
• Methamphetamine use: Similar mechanism to cocaine with severe hypertension and cardiovascular complications 3

Maternal Factors

• Tobacco smoking: OR 1.80, causes chronic placental insufficiency 3, 4
• Advanced maternal age: Associated with underlying vascular disease 4
• Thrombophilias: Predispose to microvascular thrombosis at the decidual-placental interface 4

Pregnancy-Related Factors

• Preterm premature rupture of membranes (pPROM): Significantly associated with abruption 5
• Multifetal gestation: Increased uterine distension and vascular demands 4
• Hydramnios: Overdistension of the uterus 4
• Placenta previa spectrum: Abnormal placentation increases risk 5
• Uterine malformations: Abnormal implantation sites 5
• Intrauterine infections: Inflammatory damage to decidual vessels 4

Modifiable Behavioral Factors

• Alcohol consumption: OR 2.2 for placental abruption 3
• Inadequate prenatal care: Often coexists with substance use and other risk factors 3

Important Clinical Caveats

The immediate risk of abruption increases 7.8-fold in the hour following moderate-to-vigorous physical activity in at-risk women, though habitual physical activity is actually protective compared to sedentary lifestyle. 6 This paradox suggests that acute hemodynamic stress triggers abruption in placentas already compromised by chronic pathology, rather than exercise causing the underlying problem.

Cocaine and substance use often coexist with multiple other risk factors including tobacco, alcohol, and inadequate prenatal care, creating a high-risk profile that requires universal screening. 3

Despite identified risk factors, placental abruption remains largely unpredictable and unpreventable, as the pathophysiology is incompletely understood and no clinically useful predictive biomarker exists. 2, 4