Summary Objectives: The aim of our study was to present the detailed execution and interpretation of the hyperoxygenation test in the fetus. Material and methods: This was a retrospective investigation of fetuses examined in The Department for Diagnosis and Prophylaxis of Congenital Malformations (Polish Mother’s Memorial Hospital Institute and Medical University in Lodz) between January 2006 and December 2009, in whom in addition to the routine echocardiographic examination the hyperoxygenation test was performed. Indications for such an extended evaluation were suspected fetal malformations and pulmonary hypoplasia. Changes in the fetal pulmonary circulation before and after maternal exposure to hyperoxygenated air together with the newborn follow-up were analyzed. Results: Clinical outcome was available for 42 of 52 cases: 16 patients died (including 11 cases with negative hyperoxygenation test), whereas 24 patients were discharged home (including 17 cases with positive hyperoxygenation test). The probability of survival for fetuses with the positive test was significantly higher than for fetuses with the negative one (p=0.016, Fischer’s exact test). Conclusions: Based on changes evoked in the fetal pulmonary circulation, the hyperoxygenation test seems helpful in predicting impaired fetal lung development Functional assessment of the fetal pulmonary circulation may be useful in predicting fetal lung hypoplasia and respiratory failure in the neonate.