A child was born at the 37th week of pregnancy with hydrops fetalis. Hydramnios and hydrothorax had been proven by fetal ultrasonography. No fetal or maternal etiology was found. At age 4 days, at the beginning of enteral nutrition, the pleural effusion became characteristic of chylothorax. Recovery occurred after 2 weeks of parenteral nutrition. Chylothorax might be an unrecognized etiology of non immune hydrops fetalis. The relationships between both conditions and the interest of prenatal treatment are discussed.