Fetal hydrothorax is associated with elevated perinatal mortality. Management of this condition is controversial given that in utero spontaneous resolution has been described. A case of fetal hydrothorax associated with an extralobar lung sequestration that showed pathologic cardiotocographic patterns and abnormal Doppler velocimetry indices in several fetal vascular beds in reported. All pathologic patterns improved after fetal thoracentesis. It can be concluded that monitoring fetal well-being by means of cardiotocography and Doppler velocimetry may help in timing thoracentesis in cases of fetal hydrothorax.