FETAL PLASMA IRON AND RESTORATION OF RED-BLOOD-CELL MASS AFTER HEMORRHAGE OF THE OVINE FETUS

OBJECTIVE: Our purpose was to determine whether the restoration of fet al red blood cell mass after acute hemorrhage of 40% of the fetal bloo d volume is related to fetal plasma iron concentration. STUDY DESIGN: Ten chronically catheterized ovine fetuses were monitored for 10 days beginning at 125 +/- 1 (SE) days of gestation. After a 3-day control p eriod 40% of the fetal blood was removed over 2 hours at a rate of app roximately 1 ml/min. Fetal plasma iron and erythropoietin concentratio ns, hematocrit, blood volume, and red blood cell mass were measured da ily before and for 7 days after fetal hemorrhage. Statistical analysis was by analysis of variance, correlation, and regression. RESULTS: Al though 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 ?he 7-day posthemorrhage period. On day 10 red blood cell mass correlated positively with prehemorrhag e (r = 0.74, p = 0.015) and posthemorrhage (r = 0.69, p = 0.045) plasm a iron concentration and negatively with posthemorrhage erythropoietin concentration (r = -0.68, p = 0.047). CONCLUSION: Fetal plasma iron c oncentration is an important factor in restoration of fetal red blood cell mass after loss of blood. The negative correlation of erythropoie tin concentration with posthemorrhagic red blood cell mass suggests th at iron, not erythropoietin, may be the limiting factor in recovery fr om hemorrhage-induced anemia. Thus iron supplementation of the fetus m ay be of benefit in the treatment of some types of fetal anemia.