Comparison of low- and high-altitude Doppler velocimetry in the peripheral and central circulations of normal fetuses

OBJECTIVE: Our aim was to test the hypothesis that Doppler velocimetry of the peripheral and central circulations in normal fetuses is not affected by moderately high altitude (Denver, Colo-1609 m) compared with sea level (Milan, Italy-40 m). STUDY DESIGN: One hundred nineteen patients with singleton pregnancies underwent Doppler waveform analysis of the following: umbilical artery, uterine artery, middle cerebral artery, ductus venosus, and the tricuspid and mitral valves. RESULTS: Birth weights were reduced at Denver's altitude (P < .001). The early/late diastolic inflow ratios of the atrioventricular valves increased with gestational age (P < .01), whereas systolic/diastolic ratios of the uterine and umbilical arteries decreased with gestational age (P < .01). There were no Doppler velocimetry differences in any vessel between Denver's and Milan's altitudes. CONCLUSIONS: Gestational age has the same effect on Doppler index at both high and low altitudes. Moderately high altitude does not affect uteroplacental or fetal vascular Doppler index and may reflect normal acclimatization in the smaller Denver fetuses.