Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude.
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 O(2) saturation (Sa(O2)) 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 approximately 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 Sa(O2) with the result that arterial O2 content (Ca(O2)) 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 Ca(O2) was responsible for protecting Andeans from altitude-associated reductions in fetal growth.
Vargas
Marco
M
Altitude Research Center, University of Colorado at Denver and Health Sciences Center, 4200 East Ninth Ave., Denver, CO 80262, USA.
Vargas
Enrique
E
Julian
Colleen G
CG
Armaza
J Fernando
JF
Rodriguez
Armando
A
Tellez
Wilma
W
Niermeyer
Susan
S
Wilson
Megan
M
Parra
Esteban
E
Shriver
Mark
M
Moore
Lorna G
LG
D000328:Adult; D000531:Altitude; D001724:Birth Weight / Q000502:physiology; D001784:Blood Gas Analysis; D001810:Blood Volume / Q000502:physiology; D001838:Bolivia; D005006:Ethnicity; D005060:Europe; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology; D006340:Heart Rate, Fetal / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D010100:Oxygen / Q000097:blood*; D011247:Pregnancy / Q000097:blood*; D015656:Respiratory Mechanics / Q000502:physiology
D006454:Hemoglobins; D010100:Oxygen