The Frequency Clinical Significance and Pathological Features of Chronic Chorioamnionitis: A Lesion Associated with Spontaneous Preterm Birth

摘要

Acute chorioamnionitis (ACA) is a well-established lesion of the placenta in cases with intra-amniotic infection. In contrast, the clinicopathologic significance of chronic chorioamnionitis (CCA) is unclear. This study was conducted to determine the frequency and severity of CCA in normal pregnancy and various pregnancy complications. Placentas from the following patient groups were studied: 1) term not in labor (TNL; n=100), 2) term in labor (TIL; n=100), 3) preterm labor (PTL; n=100), 4) preterm prelabor rupture of the membranes (PPROM; n=100), 5) preeclampsia at term (TPE; n=100), 6) preterm preeclampsia (PPE; n=100), and 7) small-for-gestational-age at term (SGA; n=100). Amniotic fluid CXCL10 concentration was measured in 64 patients. CXCL9, CXCL10, and CXCL11 mRNA expressions in the chorioamniotic membranes were assessed by real-time quantitative RT-PCR. The frequency of CCA in PTL and PPROM groups was 34% and 39%, respectively, which was higher than those of normal term placentas (TNL 19%, TIL 8%; p<0.05 each). The frequency of CCA in TPE, PPE and SGA groups was 23%, 16%, and 13%, respectively. Concomitant villitis of unknown etiology (VUE) was found in 38.2% and 35.9% of PTL and PPROM cases with CCA, respectively. Interestingly, the median gestational age of preterm CCA cases was higher than that of ACA cases (p<0.05). The median amniotic fluid CXCL10 concentration was higher in cases with CCA than in those without, in both PTL and PPROM groups (p<0.05 and p<0.01, respectively). CXCL9, CXCL10, and CXCL11 mRNA expression in the chorioamniotic membranes was also higher in CCA cases than in those without CCA (p<0.05). We propose that CCA defines a common placental pathologic lesion among the PTL and PPROM groups, especially in cases of late preterm birth. Its association with VUE and the chemokine profile in amniotic fluid suggests an immunological origin, akin to transplantation rejection and graft-versus-host disease in the chorioamniotic membranes.