ABSTRACT
The blood picture of Macaca fascicularis during its in utero fetal development was established by a study of 31 fetuses beginning on fetal gestation day (GD) 80 through gestation day 150 (Table 1, Tarantal 1993). A total of 68 samplings were assessed (2-5 samples per fetus). The blood samples were obtained by ultrasoundguided cardiocentesis from ketamine-immobilized (10 mg/kg, IM) females whose time of conception was systematically attested with a maximum error of 2 days. The length of pregnancy is ~165 days although it has been reported to extend to 190 days. The general pattern of the developing erythroid blood picture initiating on gestation day 80 was a steady increase in the erythrocyte count, hematocrit, and hemoglobin concentration that continued throughout gestation until a slight decline occurred in all three values close to term at about 150 days of pregnancy (Table 1). The earliest erythrogram was Rbc 3.02 × 106/µL, Hct 33.0%, and Hb 11.3 g/dL and by GD 150 the values had attained 4.03 × 106/µL, 36.7%, and 12.4 g/dL, respectively. The MCV demonstrated a gradual decline throughout the period. The earliest value was 109 fL but at close to term (150 days) it was still larger than that of the adult, that is, mean 91 fL versus the usual 70-80 fL obtained in adults. The enhanced size is a reection of multiple factors including the fact that these are a population of cells derived most likely from the liver as well as the primitive generation that originated in the yolk sac and this pool of cells has a large component of reticulocytes. The MCH demonstrated a parallel declining course illustrating the diminishing quantity of hemoglobin in smaller red cells, while the MCHC offered the consistent stable level that is typical for this parameter. The numerical occurrence of nucleated erythrocytes in the circulation was most interesting and variable. These cells were most numerous at the earliest assessment (GD 80), the mean was ~1000 per 100 circulating leukocytes. Thus, these nucleated cells were more numerous than white cells. The range observed among the subjects (n = 7) was particularly broad, 63-3500/100 wbc. Ten days later the mean dropped markedly to 300 nucleated red cells/100 leukocytes (range 0-1600, n = 12). A further reduction to a mean 63/100 wbc (range 0-300) was obtained at 110 days gestation. They were relatively rare by 140-150 days with an average incidence of 7 normoblasts per 100 leukocytes. Thus, this population persisted as a signicant component of the circulating pool of cells throughout
pregnancy because even at gestation days 140 and 150, their mean absolute level was 469 and 490 nucleated red cells per microliter of blood. As would be expected, polychromasia and anisocytosis were seen throughout gestation. Hypochromasia, poikilocytosis, and Jolly bodies were uncommon. Tarantal (1993) has underscored the near unanimity of the fetal development of hemopoiesis in man and the macaques.
