A 32-year-old multiparous woman in active labor (cervical dilation 6 cm, contractions every 2–3 minutes) reports sudden onset of severe, tearing abdominal pain and vaginal bleeding. Fetal heart rate drops from 140 to 100 bpm with late decelerations. On palpation, the uterus is tender and rigid. Which investigation is most appropriate to confirm the suspected diagnosis and guide emergency management?

Explanation

## Investigation of Choice in Suspected Placental Abruption ### Clinical Presentation The patient presents with the **classic triad of placental abruption**: 1. Sudden severe abdominal pain (uterine tenderness, rigidity) 2. Vaginal bleeding (may be concealed or revealed) 3. Fetal distress (late decelerations, bradycardia) This is a **medical emergency** requiring rapid diagnosis and delivery. ### Why Transabdominal Ultrasound is Correct **Key Point:** Transabdominal ultrasound is the **gold standard imaging investigation** to confirm placental abruption and assess: - Presence and extent of retroplacental hematoma - Fetal viability and cardiac activity - Placental location (to guide delivery approach) - Amniotic fluid volume **High-Yield:** Ultrasound findings in abruption: - Hypoechoic or isoechoic retroplacental collection (acute clot) - Placental thickening - Reduced amniotic fluid (in severe cases) - Fetal cardiac activity (confirms viability for emergency delivery planning) **Clinical Pearl:** While clinical diagnosis of abruption is often made on **clinical grounds alone** (pain + bleeding + fetal distress), ultrasound **confirms the diagnosis** and quantifies severity, guiding the urgency and mode of delivery (emergency cesarean vs. vaginal delivery if fetal distress resolves). ### Why Other Options Are Not First-Line | Investigation | Limitation | |---|---| | **Cardiotocography (CTG)** | Essential for fetal monitoring but does NOT diagnose abruption; it documents fetal distress (already evident clinically). | | **Serum fibrinogen & D-dimer** | Useful to assess for DIC (a complication of abruption) but do NOT diagnose abruption itself; results take time. | | **Speculum examination** | Does not assess placental location or retroplacental hematoma; less useful in this acute scenario. | **Mnemonic: ABRUPTION Workup — **A**bruption diagnosis = **U**ltrasound (transabdominal), **R**isk assessment = **C**oagulation labs (fibrinogen), **U**rgent delivery = **T**iming based on fetal viability. [cite:Williams Obstetrics 26e Ch 41]