Sirenomelia or mermaid syndrome is a rare and fatal congenital condition, which is not associated with chromosomal anomalies. The fusion of the lower extremities characterizes it to form one single lower limb and its aetiology remains unclear. We report a rare case of 32-year-old woman who had a successful pregnancy following in-vitro-fertilization. A first trimester scan showed decreased liquor volume therefore she was referred to fetal medicine unit for a detailed scan at 22 weeks of gestation which showed bilateral thorax hypoplasia, bilateral renal agenesis and anhydramnios. The baby was delivered with the unexpected sirenomelia congenital anomaly and died four hours after birth.