Objective: To determine whether there is a relationship between the presence of histological signs of inflammation in the extraplacental membranes and umbilical cord and the concentrations of fetal plasma interleukin-6 (IL-6).
Methods: The study examined a cohort of patients who were admitted with preterm labor or preterm premature rupture of the membranes (PROM) and who underwent cordocentesis. Inclusion criteria included fetal plasma available for IL-6 determination, histological examination of the umbilical cord and placenta, and delivery within 48 h of the procedure. This last criterion was used to preserve a meaningful temporal relationship between fetal plasma IL-6 and the results of histological examination of the placenta. Fetal plasma IL-6 was determined by a high sensitivity ELISA. Forty-five patients were available for study: 18 patients had preterm labor with intact membranes and 27 had preterm PROM.
Results: The incidence of funisitis was 44.4% (20/45): 27.8% (5/18) in patients with preterm labor and intact membranes and 55.6% (15/27) in patients with preterm PROM. The median values of fetal plasma IL-6 in patients with funisitis, chorioamnionitis without funisitis, and non-inflamed membranes were 51.4, 18.4 and 5.2 pg/ml, respectively. After log transformation of the fetal plasma IL-6 concentration, the means differed significantly from each other (ANOVA, p < 0.02). There was no difference in log fetal plasma IL-6 concentration between patients with funisitis and those with chorioamnionitis without funisitis. The difference in mean concentration of log fetal plasma IL-6 between patients with funisitis or chorionic vasculitis and those without inflammation was highly significant (post-hoc test, p = 0.01 and p < 0.01, respectively). Fetuses with fetal plasma IL-6 > 11 pg/ml had a significantly higher rate of histological signs of inflammation in the extra-placental membranes and umbilical cord than those with fetal plasma IL-6 < 11 pg/ml (funisitis: 55.6% (15/27) vs. 27.8% (5/18), p < 0.05; chorionic vasculitis: 55.6% (15/27) vs. 12.5% (2/16), p < 0.01; chorioamnionitis only: 25.9% (7/27) vs. 16.7% (3/18), p < 0.05; no inflammation: 18.5% (5/27) vs. 55.6% (10/18), p < 0.05, respectively). Fetuses with funisitis had significantly higher rates of clinical and histological chorioamnionitis, and neonatal infectious morbidity (proven + suspected sepsis) than fetuses without funisitis (40% (8/20) vs. 8% (2/25), 90% (18/20) vs. 36% (9/25), and 40% (8/20) vs. 4% (1/25), respectively; p < 0.01 for each). Fetuses with chorionic vasculitis had significantly higher rates of clinical and histological chorioamnionitis as well as neonatal infectious morbidity (proven + suspected sepsis) than fetuses without chorionic vasculitis (100% (17/17) vs. 42.3% (11/26), p < 0.01; 82.4% (14/17) vs. 50.0% (13/26), p = 0.05; and 41.2% (7/17) vs. 7.7% (2/26), p = 0.01).
Conclusion: Fetal plasma IL-6 concentration is significantly associated with the presence of inflammatory lesions in the extraplacental membranes and umbilical cord. Fetuses with fetal plasma IL-6 > 11 pg/ml had a significantly higher rate of funisitis and/or chorionic vasculitis than fetuses with fetal plasma IL-6 < 11 pg/ml. These findings suggest that funisitis/chorionic vasculitis is the histological manifestation of the fetal inflammatory response syndrome.