Effect of altitude on uterine artery blood flow during normal pregnancy

Abstract

To determine whether uterine blood flow was reduced and indexes of pelvic blood flow distribution altered in normotensive pregnancy at high (3,100 m) compared with low altitude (1,600 m), we measured uterine, common iliac, and external iliac artery blood flow velocities and diameters in women during pregnancy and again postpartum. Pregnancy increased uterine artery diameter, blood flow velocity, and volumetric flow at both altitudes. Uterine artery blood flow velocity was greater (69.0 +/- 2.2 vs. 59.4 +/- 3.0 cm/s; P < 0.005) but diameter was smaller at 3,100 m than at 1,600 m (2.5 +/- 0.3 mm vs. 3.4 +/- 0.2 mm; P< 0.005), resulting in volumetric flow that was one-third lower at week 36 of pregnancy (203 +/- 48 vs. 312 +/- 22 ml/min, respectively; P < 0.01). Pregnancy increased common iliac blood flow velocity and decreased external iliac artery blood flow velocity at both altitudes. The uterine artery received a smaller percent of common iliac flow at 3,100 than at 1,600 m (46 +/- 7 vs. 74 +/- 6%; P < 0.005). Gestational age was similar but birth weight was lower at 3,100 m than at 1,600 m. Among subjects at 1,600 m, variation in uterine blood flow velocity correlated positively with infant birth weight. We concluded that reduced uterine blood flow and altered pelvic blood flow distribution during pregnancy at high altitude likely contributed to the altitude-associated reduction in infant birth weight.

Preserved placental oxygenation and development during severe systemic hypoxia

“…Apparently, eNOS is upregulated in human placentas from high-altitude pregnancies as well (Tissot van Patot M, unpublished observation). Consistent with our results, an increase in uterine blood flow velocity, probably as a result of downstream vasodilation, has been observed in pregnant women residing at high altitude (50). Applying the NOS inhibitor L-NAME, we demonstrated the crucial role of NOS upregulation as a mechanism for preserved tissue oxygenation.…”

Effects of hypoxia on epididymal sperm parameters and protective role of ibuprofen and melatonin

“…Many other publications are concerned with fertility compromise at high altitude (Zamudio et al, 1995;Niermeyer 1999;Beall 2000;Moore et al, 2000;Crognier et al, 2002;Moore, 2003;Vitzthum and Wiley 2003;Dang et al, 2006). Acute simulated hypobaric hypoxia at extremely high altitudes results in damage to all testicular cells, including spermatogenic and somatic elements (Sertoli and Leydig cells) (Shevantaeva and Kosyuga, 2006).…”

Effects of Altitude versus Economic Status on Birth Weight and Body Shape at Birth

“…Thus, it can be inferred from past and present observations that fetal growth retardation at high altitude may occur primarily in late gestation and may reflect maternoplacental insufficiency to meet the fetal oxygen demands at this time. Potential mechanisms may include a reduction in the transplacental oxygen partial pressure gradient (56) and/or depressed uteroplacental vasodilators (57,58) leading to reduced uterine blood flow (32,59), all of which have been reported in high-altitude pregnancy. It is possible that this unmatched fetal oxygen demand may trigger the release of fetoplacental hormones and factors that control tissue accretion and differentiation in the fetus during late gestation, such as insulin, thyroxine, cortisol, and IGF (60,61).…”