A 35-year-old multiparous woman at 28 weeks gestation with chronic hypertension presents with vaginal bleeding and abdominal pain. Diagnosis of placental abruption is confirmed on ultrasound. Regarding the pathophysiology, risk factors, and investigations in abruptio placentae, all of the following are correct EXCEPT:

Explanation

## Pathophysiology, Risk Factors, and Diagnosis of Abruptio Placentae ### Risk Factors and Epidemiology **Key Point:** Hypertension (both chronic and gestational) is the **single most common modifiable risk factor** for placental abruption, accounting for 40–50% of cases. | Risk Factor | Relative Risk | Notes | |-------------|---------------|-------| | **Hypertension** | 2.5–4.0 | Most common modifiable factor | | **Smoking** | 1.5–2.0 | Dose-dependent | | **Cocaine use** | 3.0–4.0 | Acute vasospasm | | **Trauma** | 3.0–5.0 | Motor vehicle accident, domestic violence | | **Preeclampsia** | 4.0–5.0 | Severe form; endothelial dysfunction | | **Placental insufficiency** | Variable | IUGR, prior abruption | | **Thrombophilia** | 2.0–3.0 | Inherited or acquired | **High-Yield:** Prior abruption is the **strongest predictor** of recurrence (5–17% in subsequent pregnancies). ### Coagulopathy in Abruption **Clinical Pearl:** DIC occurs in approximately **10%** of clinically overt abruptions but in up to **50%** of severe, concealed abruptions. The mechanism: 1. Thromboplastin released from damaged placental tissue enters maternal circulation 2. Triggers extrinsic coagulation pathway 3. Consumption of platelets and clotting factors 4. Secondary fibrinolysis **Mnemonic: DIC in APH** — **D**amaged placenta → **I**ntrinsic **C**oagulation activation ### Investigations in Abruption **Key Point:** Diagnosis is **primarily clinical and ultrasound-based**. No single laboratory or serum marker is specific for abruption. | Investigation | Role | Interpretation | |---------------|------|----------------| | **Ultrasound** | First-line imaging | Detects ~50% of abruptions; absence does NOT exclude | | **FBC** | Baseline hemoglobin; platelet count | Serial Hb tracks blood loss; platelets assess DIC | | **Coagulation profile** (PT, aPTT, INR) | Assess DIC | Prolonged times suggest consumption | | **Fibrinogen** | Sensitive marker of DIC | < 100 mg/dL indicates severe DIC | | **D-dimer** | Nonspecific; elevated in pregnancy | Not diagnostic for abruption | | **Kleihauer–Betke / Flow cytometry** | Quantify FMH | Determines anti-D dose in Rh-negative mothers | | **Serum AFP** | **NOT specific for abruption** | Elevated in multiple conditions (neural tube defects, Down syndrome, liver disease); not used for abruption diagnosis | **Warning:** Serum AFP is a **second-trimester screening marker** for fetal anomalies and maternal conditions, **NOT** a diagnostic test for placental abruption. It has no role in abruption workup. ## Why Option 3 Is Incorrect Maternal serum AFP is **not** a specific (or even nonspecific) marker for diagnosing placental abruption. AFP is used in second-trimester screening for Down syndrome and neural tube defects. Abruption is diagnosed clinically and by ultrasound; no serum marker is specific for it.