To evaluate fetal Doppler parameters in pregnant women with influenza AH1N1 infection and reduced arterial PAO2. Fifteen pregnant patients with confirmed diagnosis of influenza AH1N1 infection were evaluated and classified according to arterial blood gas values as: group 1, reduced PAO2, (<60 mmHg); and group 2, normal PAO2 (≥60 mmHg). Doppler evaluation of the umbilical artery (UA), middle cerebral artery (MCA), ductus venosus, and myocardial performance index (MPI) were performed within 24 hours of admission, 3 days later, and 4 weeks after the first examination; the perinatal outcome was registered. No maternal or fetal deaths were documented; 5 patients presented with reduced PAO2, and 6 patients (40%) developed perinatal complications: all 5 from the group with hypoxia (uterine contractions n = 1, preterm delivery n = 2, fetal growth restriction n = 2), and one from the group with normal gas values (fetal growth restriction) (p < 0.01). Doppler parameters within 24 hours of admission and 3 days later in the hypoxia group showed: increased UA-pulsatility index (PI) (p = 0.01), reduced MCA PI (p = 0.03), and increased MPI (p = 0.02). No changes in the ductus venosus were observed (p = 0.78). Four weeks later only MCA PI in the hypoxia group was reduced (p = 0.01). Supporting information can be found in the online version of this abstract Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.