The original version of this article contained a mistake. The measurements of the lesion are given in millimetres, whereas they should in fact be in centimetres. The updated text appears below:

Fetal MRI demonstrated a cyst measuring 6.7cm×4.3cm, associated with mediastinal shift and affecting cardiac contractility. Scalp oedema and ascites noted at this time indicated evolving fetal hydrops.

At 28 weeks, thoracoamniotic shunt was inserted to drain the lesion. By 29 weeks, the cyst had decreased in size, now 5.1 cm×3.4cm. Cardiac function, oedema and ascites had all improved.