## Most Common Cause of Abruptio Placentae **Key Point:** Maternal hypertension (chronic hypertension or gestational hypertension) is the single most common identifiable cause of abruptio placentae, accounting for approximately 40–50% of cases with an identified etiology. ### Pathophysiology Hypertension causes: - Acute vasospasm and endothelial damage in placental bed vessels - Increased placental vascular resistance - Rupture of small vessels in the decidua basalis - Hemorrhage and placental separation ### Other Important Risk Factors | Risk Factor | Relative Risk | Mechanism | |---|---|---| | Maternal hypertension | 2.5–4× | Vasospasm, endothelial injury | | Placental abruption (prior) | 25× | Unknown; recurrence risk ~10% | | Maternal trauma | 5–10× | Direct mechanical disruption | | Cocaine/amphetamine use | 3–5× | Vasospasm, hypertension | | Smoking | 1.5–2× | Placental vascular dysfunction | | Polyhydramnios | 2× | Sudden decompression | | Preeclampsia/eclampsia | 2–3× | Endothelial dysfunction | **High-Yield:** In approximately 40% of abruption cases, NO identifiable cause is found — these are termed "idiopathic abruptions." **Clinical Pearl:** A history of prior abruption carries the highest recurrence risk (~10%), making it a critical screening point in subsequent pregnancies. ### Management Implication Strict blood pressure control in hypertensive pregnancies is a cornerstone of abruption prevention. [cite:Williams Obstetrics 26e Ch 34]
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