Type I fetal cystic adenomatoid malformation of the lung with hydrops at 18 weeks' gestation: a case report.

Fetal cystic adenomatoid malformation, type I, is a rare pulmonary anomaly that has been diagnosed after 20 weeks' gestation. The prognosis of this malformation is usually dependent on whether it is microcystic, types II and III, or macrocystic, type I. We report a case of severe macrocystic fetal cystic adenomatoid malformation diagnosed at 18.4 weeks' gestation. This case demonstrates that fetal cystic adenomatoid malformation can be diagnosed at 18 weeks and that hydrops with oligohydramnios may be part of the natural history of type I lesions this early in pregnancy.