Prospective cohort study about the lymphocyte subpopulations' change and impact on the pregnancy outcome in fetal growth restriction

Objective: To evaluate lymphocyte subpopulations' change and impact on the pregnancy outcome in fetal growth restriction (FGR) through a prospective cohort study. Methods: Sixty singleton pregnancies with FGR and 20 normal pregnant women were enrolled at the third trimester of pregnancy in this study. FGR was defined according to fundal height and abdominal circumference through obstetric examination and ultrasound examination. Third trimester peripheral blood and umbilical cord blood lymphocyte subpopulations were analysed by flow cytometry. The cytotoxic activity of lymphocytes using umbilical cord blood mononuclear activated kill cells as the effector cells, K562 cells as the target cells was measured by MTT deoxidation assay. Results: There were no significant differences about the age, parity, gestational age enrolled, BMI before pregnancy between the FGR and control group. The birth weight, length and head circumference of the neonates from FGR group were less than that from normal control. The percentages of B-lymphocytes in peripheral blood at the third trimester were significantly increased in FGR group compared to that in control group (P < 0.05). In umbilical cord blood, FGR group had a higher percentage of both CD3 and CD4 lymphocyte, lower absolute cell counts and percentage of B-lymphocyte, and higher CD4/CD8 ratio than control group (P < 0.05). Most importantly, the kill cell activity of the lymphocytes in cord blood from FGR group was significantly higher than that from control group (P < 0.05). The significant positive correlations were also found that the percentage and number of B lymphocytes in umbilical cord blood with birthweight, birthlength and birth head circumference, but CD4/CD8 ratio, the kill cell activity in umbilical cord blood had negative correlations with that. The percentage of B lmyphocyte in third trimester and CD4/CD8 ratio, kill cell activity in umbilical cord blood are associated with an increased risk of prematurity and SGA birth, but contrary result was found with the percentage and number of B lmyphocyte in cord blood. Conclusions: Fetal immunological rejection could be involved in the pathogenesis of FGR. The changes of T lymphocyte subpopulations and B-cells, enhanced kill cell activity might cause FGR and preterm birth.