Fetal plasma iron and restoration of red blood cell mass after hemorrhage of the ovine fetus

Abstract

Our purpose was to determine whether the restoration of fetal red blood cell mass after acute hemorrhage of 40% of the fetal blood volume is related to fetal plasma iron concentration. Ten chronically catheterized ovine fetuses were monitored for 10 days beginning at 125 +/- 1 (SE) days of gestation. After a 3-day control period 40% of the fetal blood was removed over 2 hours at a rate of approximately 1 ml/min. Fetal plasma iron and erythropoietin concentrations, hematocrit, blood volume, and red blood cell mass were measured daily before and for 7 days after fetal hemorrhage. Statistical analysis was by analysis of variance, correlation, and regression. Although blood volume was restored within 3 days of the hemorrhage (101.0% +/- 1.4% of prehemorrhage volume), red blood cell mass was not (81.8% +/- 2.8%). Only 6 of 10 fetuses restored their red blood cell mass to prehemorrhage levels by the end of the 7-day posthemorrhage period. On day 10 red blood cell mass correlated positively with prehemorrhage (r = 0.74, p = 0.015) and posthemorrhage (r = 0.69, p = 0.045) plasma iron concentration and negatively with posthemorrhage erythropoietin concentration (r = -0.68, p = 0.047). Fetal plasma iron concentration is an important factor in restoration of fetal red blood cell mass after loss of blood. The negative correlation of erythropoietin concentration with posthemorrhagic red blood cell mass suggests that iron, not erythropoietin, may be the limiting factor in recovery from hemorrhage-induced anemia. Thus iron supplementation of the fetus may be of benefit in the treatment of some types of fetal anemia.