Objective: Preterm birth rate in the United States is higher in blacks than whites. It has been hypothesized that a differential inflammatory response may explain this disparity. The objective of this study is to examine the inflammatory cytokine, tumor necrosis factor (TNF)-alpha and soluble TNF receptor concentrations (sTNFR1 and sTNFR2) in the amniotic fluid of black and white women at delivery.
Study design: Amniotic fluid samples were collected during active labor from 158 cases (preterm births, gestational age 22(0/7) weeks to 36(0/7) weeks, 52 black and 106 white) and 175 controls (term births, gestational age 37(0/7) weeks to 42(0/7) weeks, 87 black and 88 white) at Centennial Women's Hospital, Nashville, TN. Amniotic fluid TNF-alpha, sTNFR1, and sTNFR2 concentrations and the molar ratios of TNF-alpha to its receptors were compared between cases and controls within each racial group.
Results: Median TNF-alpha concentration was associated with preterm birth when whites and blacks were analyzed together, with cases having higher values (191.5 pg/mL) than controls (68.9 pg/mL; P < .001). There were no significant associations with sTNFR1 or sTNFR2 concentrations between cases (2409.4 and 2934.3 pg/mL, respectively) and controls (2759.9 and 3084.1 pg/mL, respectively) when the racial groups were analyzed together (P = .08, P = .4, respectively). Black cases associated with higher TNF-alpha concentrations (1287.0 pg/mL in cases and 67.3 pg/mL in controls; P < .001). In whites there was no association between TNF-alpha and preterm birth (P = .3). The molar ratio of TNF-alpha/total sTNFR (R1 plus R2) associated with higher TNF-alpha in black cases, compared with black controls (P < .001). There was no significant association between white cases and controls for ligand receptor ratios (P = .3).
Conclusion: The TNF-alpha/sTNFR profile in pregnancy differs between racial groups, suggesting a difference in bioavailability of TNF-alpha. The larger molar ratio of TNF-alpha/sTNFR in black cases may be indicative of a TNF-alpha mediated pathological process of preterm birth in blacks but not in whites.