A 28-year-old primigravida from Delhi presents at 18 weeks of gestation with vaginal spotting and mild lower abdominal pain. Ultrasound reveals a dichorionic diamniotic twin pregnancy with a live fetus in each sac. However, one twin shows an empty gestational sac with no yolk sac or fetal pole. The patient is hemodynamically stable and has no fever. What is the most appropriate management at this stage?

Explanation

## Clinical Context This case describes a **vanishing twin syndrome** in a dichorionic diamniotic twin pregnancy — one twin has failed to develop (blighted ovum) while the other is viable. ## Management Principles **Key Point:** In dichorionic diamniotic pregnancies with one viable and one non-viable twin, expectant management is the standard approach in the absence of maternal complications. **High-Yield:** Vanishing twin syndrome occurs in 20–50% of multiple pregnancies diagnosed in the first trimester. The non-viable twin is typically resorbed or becomes a fetus papyraceus without significant maternal morbidity in dichorionic pregnancies. ### Why Expectant Management? 1. **Dichorionic separation** — the failed twin is in a separate sac with its own placenta; risk of maternal infection is low 2. **Viable co-twin** — continuing the pregnancy allows the normal fetus to develop to viability 3. **No maternal systemic signs** — patient is afebrile and hemodynamically stable 4. **Natural resorption** — the blighted ovum will typically be resorbed or compressed into a fetus papyraceus ### Counselling Points - Increased risk of preterm labor (relative to singleton pregnancy) - Slightly increased perinatal mortality in the surviving twin - No increased risk of congenital anomalies in the surviving twin - Serial ultrasound to confirm viability of the remaining fetus and monitor growth **Clinical Pearl:** In **monochorionic** pregnancies with one non-viable twin, the risk of maternal coagulopathy and fetal complications is much higher, and selective feticide or early delivery may be considered — but this is dichorionic, making expectant management safe. ## Why Not the Other Options? - **Termination of entire pregnancy** — unjustified when one twin is viable and mother is well - **Selective feticide** — not indicated in the absence of maternal infection or fetal anomaly in the surviving twin - **Induction at 20 weeks** — premature delivery of a viable fetus carries high neonatal morbidity/mortality; no maternal indication present