Impact of Race and Gestational Age on Red Blood Cell Indices in Very Low Birth Weight Infants

Abstract

Background. Normative data for hematologic values in the very low birth weight infants are limited and inconsistent, with the reported mean hematocrit (HCT) in these infants ranging from 43.5% to 60%. No data are available on the effect of race. Objectives. To establish normative data for hemoglobin (Hb) and HCT by arterial sampling obtained during the first 3 hours after birth in black and white premature infants ≤31 weeks of gestation. Methods. Retrospective chart review of all infants ≤ 31 weeks of gestation born between June 1994 and October 1998. Inclusion criteria: infant ≤31 weeks of gestation who had an arterial blood sample obtained in the first 3 hours after birth. Exclusion criteria: infants were excluded if they had any medical condition that may affect the red blood cell indices (eg, twin-to-twin transfusion or fetomaternal hemorrhage). Results. Of 428 infants, 188 who met both inclusion and exclusion criteria were classified into 3 gestational age groups: group 1 = 23 to 25 weeks of gestation (n = 40); group 2 = 26 to 28 weeks (n = 60); and group 3 = 29 to 31 weeks (n = 88). There were statistically significant differences between groups 1 and 3 in HCT, Hb, mean corpuscular Hb (MCH), and mean corpuscular volume (MCV). No differences in HCT and Hb values were noted in relation to sex, mode of delivery, multiple gestation, antenatal steroids, or maternal smoking. In group 3, the mean Hb, HCT, and MCV values were higher in white infants than in black infants (16.7 ± 1.6 g/dL vs 15.4 ± 1.7 g/dL; 50.0 ± 5.0 vs 45.5 ± 4.6; and 112 ± 5 fL vs 107 ± 8 fL, respectively). Conclusions. Hb, HCT, and MCH values are described for premature infants ≤31 weeks of gestation born in North America. Hb and HCT increased, whereas MCV decreased with gestational age. Hb, HCT, and MCV values are statistically higher in white infants than in black infants.