AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 5 1075-R1083, Copyright © 1991 by American Physiological Society
Chronic anemia in pregnant ewes: maternal and fetal effects
D. Mostello, C. Chalk, J. Khoury, C. E. Mack, T. A. Siddiqi and K. E. Clark
Department of Obstetrics and Gynecology, University of Cincinnati Medical Center, Ohio 45267.
To examine maternal and fetal responses to a sustained reduction in
maternal hematocrit during days 110-138 of ovine gestation, 22 ewes and
their singleton fetuses were instrumented. By repetitive exchange
transfusions, the hematocrit in 12 ewes was decreased from 28.1 +/- 0.8
(baseline, day 110) to 14.0 +/- 0.7% (day 117) and maintained at that
level. Anemic ewes demonstrated a transient increase in heart rate from 99
+/- 4 to 116 +/- 4 beats/min and a sustained increase in cardiac output
from 117 +/- 8 to 153 +/- 11 ml.min-1.kg-1 compared with control animals.
Uterine blood flow steadily increased in control animals from 868 +/- 100
(day 110) to 1,410 +/- 177 ml/min (day 138) but failed to increase in the
anemic ewes. Uterine oxygen delivery fell from 83 +/- 10 to 39 +/- 4 ml/min
with production of anemia and remained low in the anemic ewes. Arterial PO2
and oxygen content in the fetuses of anemic ewes fell transiently below
control values (19.9 +/- 0.8 vs. 23.4 +/- 1.0 mmHg and 5.3 +/- 0.3 vs. 6.8
+/- 0.4 ml/dl, respectively) but did not persist. Fetal weights at 138 days
gestation were lower in the anemic group (2,596 +/- 329 vs. 4,313 +/- 132
g). We conclude that chronic maternal anemia results in a decreased uterine
blood flow as well as decreased uterine oxygen delivery. The fetus responds
with decreased growth but does not develop sustained hypoxia or acidosis.
