A 32-year-old primigravida at 28 weeks gestation presents with vaginal bleeding and abdominal pain. On examination, the uterus is tender and board-like. Fetal heart rate is 80 bpm. Which single clinical feature best distinguishes abruptio placentae from placenta previa?

## Distinguishing Abruptio Placentae from Placenta Previa ### Key Discriminating Feature **Key Point:** Uterine tenderness and board-like rigidity (tetanic contraction) is the hallmark of abruptio placentae and is ABSENT in placenta previa. ### Comparative Table | Feature | Abruptio Placentae | Placenta Previa | |---------|-------------------|------------------| | **Vaginal bleeding** | May be absent (concealed) or revealed | Always present (revealed) | | **Abdominal pain** | Present (often severe) | Absent | | **Uterine tenderness** | **Present — board-like rigidity** | Absent | | **Uterine contractions** | Frequent, painful, tetanic | Absent or mild | | **Fetal heart rate** | Often abnormal (bradycardia, decelerations) | Usually normal initially | | **Onset** | Sudden, any trimester (>20 wks) | Gradual, third trimester | | **Maternal shock** | Common (even with modest bleeding) | Rare unless massive bleed | ### Clinical Pearl **Clinical Pearl:** The "board-like" or "woody" uterus in abruptio placentae results from tetanic uterine contractions and extravasation of blood into the myometrium. This physical finding is pathognomonic and distinguishes it from the soft, non-tender uterus of placenta previa. ### High-Yield Mnemonic **Mnemonic:** **ABRUPTION = Acute, Board-like, Rupture of placenta, Uterine tenderness, Pain, Tetanic contractions, Intrauterine bleeding, Often concealed, Negative fetal heart rate** ### Why This Matters in Exams **High-Yield:** Examiners frequently test the ability to distinguish these two causes of APH because: 1. Both present with bleeding in pregnancy 2. Management differs fundamentally (abruptio = emergency delivery; previa = expectant care if stable) 3. The clinical examination (uterine tenderness) is the key bedside discriminator before imaging ### Pathophysiology In abruptio placentae, premature separation of the normally implanted placenta causes: - Disruption of maternal blood vessels - Accumulation of blood in the intervillous space (revealed) or behind the placenta (concealed) - Myometrial irritation → tetanic contractions → board-like uterus - Tissue factor release → DIC in severe cases