Regarding the pathophysiology and clinical features of abruptio placentae, all of the following are recognized associations EXCEPT:

Explanation

## Risk Factors and Epidemiology of Abruptio Placentae **Key Point:** Abruptio placentae is NOT more common in multiparous women; in fact, **primigravidas have an INCREASED risk** compared to multiparous women. This is a high-yield distinction. ### Risk Factors for Abruption | Risk Factor | Mechanism | Strength of Association | |---|---|---| | **Maternal hypertension** | Placental ischemia, endothelial injury | **Most common** (~40% of cases) | | **Maternal trauma** | Direct placental injury, shear forces | Well-established | | **Smoking** | Vasoconstrictive effects, impaired placental perfusion | Dose-dependent | | **Cocaine use** | Acute vasospasm, hypertension, placental infarction | Strong | | **Primigravidity** | Unknown mechanism; may relate to uterine factors | **Increased risk** | | **Multiparity** | Protective effect (lower risk with increasing parity) | Inverse relationship | | **Preeclampsia** | Endothelial dysfunction, placental pathology | 5–10× increased risk | | **Placental abruption history** | Recurrence risk ~10–17% in subsequent pregnancies | Very high | **High-Yield:** The parity relationship is **inverse**: primigravidas > multipara. This contradicts the stem's claim. ### Why the Other Options Are Correct **Maternal Hypertension:** - Present in 40–50% of abruption cases - Mechanism: placental ischemia, acute vasospasm, endothelial injury - Both chronic hypertension and gestational hypertension/preeclampsia increase risk **Maternal Trauma:** - Motor vehicle accidents, falls, intimate partner violence - Direct blunt force to abdomen → placental shear injury - Can occur at any gestational age **Smoking & Cocaine:** - **Smoking:** dose-dependent risk; impairs placental perfusion - **Cocaine:** acute hypertension + vasospasm + placental infarction **Clinical Pearl:** A primigravida with abruption should raise suspicion for preeclampsia, hypertension, or trauma as the underlying cause. [cite:Williams Obstetrics 26e Ch 34; ACOG Practice Bulletin #76]