Newborn lymphocyte subpopulations: the influence of labor.

Cord blood mononuclear cell subsets were enumerated in 31 neonates delivered after maternal labor, in 25 neonates delivered by cesarean section without preceding labor, and in 60 healthy adults. In neonates born with and without preceding labor percentages of CD3 cells were lower than those in adults (63% and 60% as opposed to 83% in adults). However, the absolute numbers of CD3 cells were significantly greater in newborn infants delivered without preceding labor (3.287 +/- 1.451 cells per microliter) than in both neonates born after labor (2.660 +/- 800 cells per microliter) and in adults (2.189 +/- 807 cells per microliter). The increase in CD3 cells in infants delivered without preceding labor reflects increased numbers of CD4-positive cells. This increase in the absolute number of T lymphocytes and CD4 (helper) lymphocytes was significant (p less than 0.02). These data indicate that labor-related stress significantly decreases the total number of neonatal T lymphocytes and the CD4 (helper) T-cell subpopulation in cord blood.