Effects of altitude changes on Doppler flow parameters for uterine, umbilical, and mid-cerebral arteries in term pregnancy: A pilot study.

OBJECTIVE We hypothesized that maternal and fetal circulations may be affected by moderately high altitudes. Therefore, we compared the differences in maternal and fetal Doppler flow parameters in women with term pregnancy living at a moderately high altitude (1890 m in Erzurum) with those of women living at the sea level (31 m in İstanbul). MATERIAL AND METHODS Eighty women (n=40, for each group) with full-term and singleton pregnancies underwent Doppler waveform analysis, and the pulsatility and resistance index values for the uterine, umbilical, and mid-cerebral arteries were recorded. Also, sex, birth, and placental weights during delivery were obtained from the medical records. RESULTS Similar mean placental weight values were found at the sea level compared with the moderately high altitude (p>0.05). The mean birth weight values were found to be lower at the moderately high altitude than those at the sea level (p<0.05). The pulsatility and resistance index values for the umbilical and mid-cerebral arteries were found to be similar between the groups (p>0.05). However, the pulsatility and resistance index values for both the right and left uterine arteries were higher at the sea level than those at moderately high altitude (p<0.05, for all). CONCLUSION Moderately high altitude does not affect fetal vascular Doppler parameters. However, it appears to increase the uterine artery blood flow bilaterally, and these alterations in the bilateral uterine artery blood flow may be associated with a physiological adaptation to high altitude.