The effect of altitude on the umbilical artery Doppler resistance.

This study examined whether there were differences between the umbilical artery systolic-diastolic (S/D) ratio and resistance index (RI) in patients with normal fetuses living at sea level (group I) and those living between 4,200 and 4,500 feet above sea level (group II). Linear regression demonstrated a significant association (P less than 0.001) between gestational age and the S/D ratio and RI for groups I (n = 100) and II (n = 128). Least-squares regression analysis demonstrated no significant differences in slopes or intercepts between groups I and II. The results would suggest that altitude, up to 4,500 feet above sea level, does not affect umbilical artery Doppler resistance in normal fetuses.