A 32-year-old multiparous woman (G3P2) with Rh-negative blood group is at 28 weeks of gestation. Routine antenatal screening shows an indirect Coombs test (ICT) titre of 1:64 with anti-D antibodies. Ultrasound reveals mild fetal ascites and hepatomegaly. Amniocentesis is performed and ΔOD450 is plotted in zone 2 of the Liley chart. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Analysis This is a case of **severe Rh isoimmunisation** with: - High antibody titre (1:64) indicating significant sensitisation - Ultrasound signs of fetal hydrops (ascites, hepatomegaly) - ΔOD450 in **zone 2** of the Liley chart at 28 weeks ## Understanding the Liley Chart **Key Point:** The Liley chart (used before 34 weeks) divides fetal prognosis into three zones based on ΔOD450: | Zone | ΔOD450 Level | Fetal Status | Management | | --- | --- | --- | --- | | **Zone 1** (Lower) | Low | Unaffected or mildly affected | Observe, repeat in 1 week | | **Zone 2** (Middle) | Intermediate | Moderately affected | IUT indicated; repeat in 1–2 weeks | | **Zone 3** (Upper) | High | Severely affected/at risk of death | IUT urgently; may need delivery if >34 weeks | **High-Yield:** Zone 2 at 28 weeks = **intrauterine transfusion is indicated**. The presence of fetal hydrops (ascites, hepatomegaly) confirms moderate-to-severe anaemia and supports the need for IUT. ## Intrauterine Transfusion (IUT) **Mnemonic:** **IUT PROTOCOL** — Indicated in zone 2–3; Ultrasound-guided needle into fetal peritoneal cavity or umbilical vein; Transfuse Rh-negative, CMV-negative, irradiated packed RBCs; Repeat every 2–3 weeks until fetal maturity or delivery. ### IUT Technique - **Intraperitoneal transfusion (IPT):** Needle placed into fetal peritoneal cavity; red cells absorbed via lymphatic system; used when cordocentesis is technically difficult - **Intravascular transfusion (IVT):** Direct transfusion into umbilical vein; more effective; preferred when feasible **Clinical Pearl:** IUT can be repeated every 2–3 weeks. The interval depends on the rate of haemolysis and fetal tolerance. Serial amniocentesis is performed to reassess ΔOD450 and guide the need for repeat transfusion. ## Why IUT Now? 1. **Zone 2 ΔOD450** = moderate fetal anaemia; risk of progression to zone 3 (fetal death) 2. **Fetal hydrops present** = evidence of severe anaemia and cardiac compromise 3. **28 weeks gestation** = too early for safe delivery; IUT is the life-saving intervention 4. **High antibody titre (1:64)** = rapid haemolysis expected; IUT prevents fetal death **High-Yield:** IUT has reduced perinatal mortality from Rh disease from >50% to <5% in appropriately managed cases.