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(−)