Newborns with intrauterine growth retardation (IUGR) often have evidence of chronic intrauterine hypoxia and compensatory erythropoiesis, as seen by increased numbers of circulating nucleated erythrocytes (NRBC) at birth. Because erythrocytes, granulocytes, and platelets are derived from a common pluripotent stem cell line, we hypothesized that increases in erythropoiesis would be accompanied by declines in leukopoiesis and thrombopoiesis. To avoid confounding perinatal factors that may differentially affect the various hematologic components, we compared postnatal absolute NRBCs (ANRBC), leukocytes (WBC), absolute granulocytes (AGC), hematocrits, and platelets(PLT) obtained in the first 6 hours of life in 13 twin/triplet multiples ≤ 36 weeks with one SGA (birthweight < 10% ile) member. We excluded sets with twin-twin transfusion (monochorionic and difference in HCT ≥.15), hemolysis, severe IVH, or chromosomal anomalies. Statistical analyses used paired Wilcoxon test between each SGA infant and either his/her AGA twin or the mean values of his/her triplet siblings, as well as linear regression analysis.

Results (mean ± 1 SD): Table

Table 1 No caption available.
Full size table

Only PLT correlated inversely with ANRBC (R square = 15.7%, P < 0.045).

Conclusions: At birth, preterm SGA newborns had increased circulating NRBCs and decreased WBC, AGC, and PLT counts when compared to their “control” AGA siblings.

Speculation: SGA fetuses “shift” stem cell differentiation towards erythropoiesis, at the expense of granulopoiesis and thrombopoiesis.