Doppler flow parameters for uterine, umbilical and midcerebral arteries at low and moderately high altitudes

Objectives 

This study aimed to investigate the differences in maternal and foetal Doppler flow parameters in women with term pregnancy living at moderately high with those of women living at sea level. For this purpose, we compared the pulsatility (PI) and resistance (RI) index values for uterine, umbilical and mid cerebral arteries in term pregnant women at moderately high altitude and sea level. Also, we aimed to investigate the differences in birth and placental weights between moderately high and low altitudes.

Methods

Eighty women between 20-40 years with full-term pregnancies (≥ 37 gestational weeks) admitted to the Obstetric Department of two institutes (40 in Nenehatun Hospital, Erzurum Turkey; 1890 m above the sea level and 40 in Bezmialem Vakif University, Istanbul, Turkey; 31 m above the sea level) for the control were enrolled in this study. All women were ethnic Turkish and permanently resident at the altitude. Initially, last menstrual period was questioned and ultrasonographic evaluation was performed to confirm gestational age and to detect foetal abnormalities. Eighty women (n=40, for each group) underwent Doppler waveform analysis and the pulsatility and resistance index values for uterine, umbilical and mid cerebral arteries were recorded. Also; sex, birth and placental weights in delivery were obtained from the medical records. Data were analysed using SPSS software 12.0 (SPSS Inc., Chicago, IL, USA) and expressed as mean ± standard deviation, P < 0.05 was considered significant. The Kolmogorov-Smirnov test was used to test for normality of variables. If data was not normally distributed, comparisons were determined using Mann-Whitney U-test. Comparisons were determined using the independent samples t-test when the data was normally distributed and Fisher’s exact test was used to compare the percentage values.

Results

There were no differences in clinical characteristics between the groups (Table 1). Doppler flow parameters, mean birth and placental weights in groups were presented in Table 2. Similar mean placental weight values were found at the sea level compared to the values at moderately high altitude (P > 0.05). A significant lower birth weight was noted at moderately high altitude in comparison with the sea level (P < 0.05). Both groups had similar PI and RI values for umbilical and mid cerebral arteries (P > 0.05). However, PI and RI values for both right and left uterine arteries were higher at the sea level than at moderately high altitude (P < 0.05, for right uterine artery PI; P < 0.01, for others) (Table 2).

Conclusions 

We suggested that altitude appears to increase the uterine artery blood flow bilaterally and these alterations in bilateral uterine artery blood flow may be associated with a physiological adaptation to chronic hypoxia. The inability of this adaptation may result in an increase in the incidence of pregnancy-related complications at high altitude.

Keywords

Doppler, altitude, pregnancy

	File/Dsecription
	Table 1 There were no differences in clinical characteristics between the groups (Table 1).
	Table 2 *P < 0.05; **P < 0.01, compared with moderately high altitude group.