Antenatally detected ovarian cyst. Transverse scan (A) at 28 weeks showing a simple cyst (4.5x3.8 cm) located in the left side of the abdomen, bulging through the anterior abdominal wall. Transverse and longitudinal scans at 34 weeks (B) show the cyst (5.5x4.8 cm) located in the right side of the abdomen. Sonogram at 37 weeks (C) showing a fluid-debris level in the cyst suggestive of cyst torsion. Scan at 38 weeks of gestation (D) showing dystrophic calcification in the cyst wall (arrow). Visualisation of the enlarged (8 mm) cystic left ovary, contralateral to the ovarian cyst, not only confirmed the diagnosis but it also disclosed the side of the origin of the cyst.