The Cystic Adenomatoid Malformation (CCAM) of the lung is rare with a frequency estimated between 1/25 000 and 1/35 000 of pregnancies. It consists of a default of alveoli development associated with an abnormal proliferation of terminal bronchioles giving rise to various sizes of cysts. We report a case of cystic adenomatoid malformation type II of the left lower lobe revealed at 22 weeks of gestation by an acute hydramnios. The fetal karyotype was normal. The presence of fetal anasarca and the severity of the adjacent organs compression have justified the pregnancy interruption which has been strongly recommended by the couple. The autopsy confirmed the diagnostic of cystic adenomatoid malformation associated with a complete hypoplasic right lung.