| dc.description.abstract | High altitude decreases birth weight,
but this effect is diminished in long vs. short-resident, high-altitude
populations. We asked whether women from long vs. short-resident,
high-altitude populations had higher arterial oxygenation levels by
comparing 42 Andean and 26 European residents of La Paz, Bolivia
(3,600 m), serially during pregnancy (weeks 20, 30, and 36) and again
4 mo postpartum. Pregnancy raised hypoxic ventilatory sensitivity
threefold, resting ventilation (VE), and arterial O2
saturation (Sao2) in both groups. Ancestry, as identified using 81 genetic markers, correlated
with respiratory pattern, such that greater Andean ancestry was
associated with higher respiratory frequency and lower tidal volume.
Pregnancy increased total blood and plasma volume 40% in both
groups without changing red blood cell mass relative to body weight;
hence, hemoglobin fell. The hemoglobin decline was compensated for
by the rise in VE and SaO2 with the result that arterial O2 content
(Cao2) was maintained near nonpregnant levels in both groups. Birth
weights were similar for all Andean and European babies, but after
adjusting for variation in gestational age, maternal height and parity,
Andeans weighed 209 g more than Europeans. Babies with heavier
birth weights and greater ponderal indices were born to Andean
women with higher VE during pregnancy. We concluded that while
maternal VE and arterial oxygenation were important, some factor
other than higher CaO2 was responsible for protecting Andeans from
altitude-associated reductions in fetal growth. | |
