Lymphocyte subsets in cord blood of preterm infants: Effect of antenatal steroids

The objective of this study was to evaluate prospectively the influence of gestational age (GA) and short-term antenatal steroids on total lymphocyte count and lymphocyte subsets in cord blood from preterm infants. Two-color flow cytometric analyses of lymphocyte subsets were performed on cord blood collected from 67 infants. These infants were grouped according to GA: group I (term, n = 19); group II (GA 33-37 weeks, n = 25); group III (GA < 33 weeks, n = 23). The mean absolute lymphocyte counts (ALC) in groups I, II and III were 5.6 ± 2.5 x 10³/μl, 4.3 ± 1.5 x 10³/μl and 3.5 ± 1.8 x 10³/μl respectively. The mean values for CD4+ lymphocytes in groups I, II and III were 2.7 ± 0.8 x 10³/μl, 2.0 ± 0.8 x 10³/μl and 1.6 ± 0.9 x 10³/μl respectively. Mean values for CD8+ lymphocytes were 0.9 ± 0.3 x 10³/μl, 0.6 ± 0.3 x 10³/μl and 0.5 ± 0.3 x 10³/μl respectively. With decreasing GA, there was a statistically significant decrease in ALC (p = 0.0035), CD4+ lymphocytes (p = 0.0013) and CD8+ lymphocytes (p = 0.0064). We then evaluated the effect of antenatal steroids, now routinely administered to women with preterm onset of labor to facilitate fetal lung maturation, and found that after adjusting for GA, infants of women on antenatal steroids had significantly fewer ALC (p = 0.0001), CD4+ lymphocytes (p = 0.02) and CD25+ lymphocytes (p = 0.03). In this population of infants, the decreased number of lymphocytes seen at younger GAs is associated with antenatal steroid use.