Preterm labor and preterm premature rupture of membranes have a different pattern in the involved compartments of acute histologoic chorioamnionitis and/or funisitis: Patho-physiologic implication related to different clinical manifestations.

It is unknown whether histo-topographic findings about the involved compartments (i.e., choriodecidua, amnion, chorionic-plate) of acute-histologic chorioamnionitis (acute-HCA) and/or funisitis according to the presence or absence of intra-amniotic inflammation (IAI) and/or fetal inflammatory response syndrome (FIRS) are different between preterm labor and intact membranes (PTL) and preterm premature rupture of membranes (preterm-PROM). The involved compartments of acute-HCA and/or funisitis were examined in 161 singleton preterm-births (<34 weeks) due to PTL (n = 88) and preterm-PROM (n = 73). The study-population was divided into IAI(-)/FIRS(-), IAI(+)/FIRS(-), and IAI(+)/FIRS(+) groups according to the presence or absence of IAI (amniotic-fluid MMP-8 ≥ 23 ng/ml) and/or FIRS (umbilical-cord plasma CRP ≥ 200 ng/ml). Histological inflammation was not detected in any-compartment except choriodecidua in IAI(-)/FIRS(-) group with PTL while inflammation appeared in all-compartment0s (choriodeciduitis-46.2 %; amnionitis-23.1 %; funisitis-30.8 %; chorionic-plate inflammation-7.7 %) in IAI(-)/FIRS(-) group with preterm-PROM. IAI(+)/FIRS(-) group had a significantly higher frequency of inflammation in each-compartment than IAI(-)/FIRS(-) group in PTL (each-for P < 0.01), but not preterm-PROM (each-for P > 0.1). However, IAI(+)/FIRS(+) group had a significantly higher rate of inflammation in each compartment than IAI(+)/FIRS(-) group in both PTL and preterm-PROM (each-for P < 0.05). We first demonstrated that PTL and preterm-PROM had a different pattern in the involved compartments of acute-HCA and/or funisitis in the IAI(-)/FIRS(--) group and in the change of involved compartments from IAI(-)/FIRS(-) to IAI(+)/FIRS(-).