The distribution of major lymphocyte subsets in cord blood is associated with its pH

Objectives: To assess in venous cord blood the distribution of major lymphocyte subsets according to pH and medications used during labor. Design and methods: Venous cord blood was sampled immediately after labor from 70 newborns (35 males and 35 females) delivered vaginally. Lymphocytes were immunophenotyped by flow cytometry and pH was measured using the AVL 900 automated blood gas analysis system. Data on birth weight, gestational age at delivery, length of labor, presence of stained amniotic fluid, medications used during labor, maternal risk factors, age and parity were collected. Results: The percentage of T lymphocytes decreased while the percentage of NK lymphocytes increased with decreasing pH over the whole range of pH values. The proportions of T and NK lymphocytes were associated with the administration of neuroplegics, spasmolytics or dihydroergotoxin in the first stage of labor. Conclusions: Cord blood pH and labor-associated variables should be taken into account to adequately interpret the profile of major lymphocyte subsets as a marker of the effect of different prenatal factors on the immune system of neonates.