Objective: Our objective was to determine if labor (term and preterm) and microbial invasion of the amniotic cavity were associated with changes in amniotic fluid concentrations of tumor necrosis factor.
Study design: Amniotic fluid was retrieved by transabdominal amniocentesis from 269 women in the following groups: midtrimester (n = 38), preterm labor with intact membranes (n = 52), preterm premature rupture of membranes (n = 74), term in active labor (n = 84), and term not in labor (n = 21). Fluid was cultured for aerobic and anaerobic bacteria and for Mycoplasma species. Tumor necrosis factor was measured with a commercially available enzyme-linked immunosorbent assay validated for amniotic fluid (sensitivity 60 pg/ml).
Results: Amniotic fluid from pregnant women in the second and third trimesters who were not in labor did not contain tumor necrosis factor. Among women in preterm labor, 92.3% (12/13) of patients with a positive amniotic fluid culture had detectable tumor necrosis factor in the amniotic fluid (median 820 pg/ml, range less than 60 to 2340 pg/ml). In contrast, only 10.2% (4/39) of women with a negative amniotic fluid culture had detectable tumor necrosis factor. Histopathologic chorioamnionitis was found in all patients who had a positive amniotic fluid culture, and tumor necrosis factor was detectable in the amniotic fluid of all but one of these patients. Among women in active labor at term, 25% (21/84) had detectable tumor necrosis factor in the amniotic fluid. Tumor necrosis factor was detected more frequently in the amniotic fluid of patients with a positive amniotic fluid culture than in patients with a negative culture (46.6% [7/15] vs 20.2% [14/69], p = 0.047). Amniotic fluid concentrations of tumor necrosis factor were significantly higher in patients with preterm premature rupture of membranes, labor, and a positive amniotic fluid culture than in the other subgroups of patients with preterm premature rupture of membranes.
Conclusion: Parturition in the setting of microbial invasion of the amniotic cavity is associated with activation of the cytokine network as demonstrated by the detection of tumor necrosis factor in human amniotic fluid.