Soluble tumor necrosis factor receptors in maternal plasma and second-trimester amniotic fluid

OBJECTIVES: We assessed maternal plasma and second-trimester amniotic fluid for levels of the p55 and p75 soluble tumor necrosis factor receptors. STUDY DESIGN: Blood was drawn from 61 healthy pregnant women (group A) before second-trimester genetic amniocentesis, and an aliquot of amniotic fluid was also obtained for this study. An additional blood sample was obtained from 13 of these patients at 36 to 40 weeks' gestation. Twenty-three healthy, nonpregnant women of reproductive age donated blood as a control group (group B). All plasma and amniotic fluid specimens were collectively assayed for the p55 and p75 soluble tumor necrosis factor receptors by specific enzyme-linked immunoassays. Additionally, tumor necrosis factor-α concentrations were measured in second-trimester plasma and amniotic fluid of 22 patients in group A and in all 23 of the nonpregnant women. RESULTS: The p55 and p75 soluble tumor necrosis factor receptors were detectable in all plasma samples from both groups of patients. The concentrations of both soluble receptors were significantly higher in second-trimester plasma compared with nonpregnant measurements (p < 0.01), and the plasma concentrations of both soluble receptors increased significantly from the second to third trimester (p < 0.01). The p55 and p75 soluble tumor necrosis factor receptors were also detectable in all amniotic fluid samples. Tumor necrosis factor-α was detected in the plasma of 15 of 22 patients in the second trimester but in none of the amniotic fluid samples and in none of the plasma saples from the nonpregnant cohort. CONCLUSIONS: Both the p55 and p75 soluble tumor necrosis factor receptors are physiologic constituents of second-trimester maternal plasma and amniotic fluid. Concentrations are elevated in pregnancy and further increase from the second to third trimester.