Transient severe unilateral and subsequent bilateral primary fetal hydrothorax with spontaneous resolution at 34 weeks' gestation associated with normal neonatal outcome

Unilateral primary fetal hydrothorax with spontaneous resolution is a rare occurrence. We present a case in which severe unilateral primary fetal hydrothorax was visualized at 28 weeks' gestation. Two weeks later bilateral primary fetal hydrothorax was documented. Ultrasonographic follow-up demonstrated further dynamic changes in the fetal condition, with an isolated unilateral hydrothorax 1 week later and subsequent complete resolution at 34 weeks' gestation. Delivery resulted in a normal neonate with no signs of pulmonary hypoplasia.