Histologic chorioamnionitis: different histologic features at different gestational ages.

Objective: The aim of this study was to investigate the rate of the different histological chorioamnionitis (HCA) grade in relation to the gestational age in term and preterm delivery.

Methods: Three hundred and ninety-two women with singleton pregnancy with spontaneous onset of labor either prematurely or at term, with histologic diagnosis of HCA, were enrolled. Placentas were classified as: deciduitis and/or histologic chorioamnionitis within the membranes (HCA1); amnionitis or inflammation of the chorionic plate without funisitis (HCA2); and histologic chorioamnionitis with funisitis (HCA3). Microbiological culture was performed on both placental and fetal membrane samples.

Results: HCA1 was more frequent in women delivering at term than in preterm (p < 0.001). HCA2 was more represented in women delivering between 32 and 36 weeks (p < 0.001) and HCA3 occurred more frequently in those delivering within 32 weeks (p < 0.001). The positive bacterial culture was higher (p = 0.008) in presence of HCA3 in comparison with HCA1 and HCA2.

Conclusions: This study showed a significantly different distribution of HCA grades in relation to gestational age at delivery. HCA may represent the expression of different subtending etiologies and may also reflect specific immune competence of gestational tissues at different gestational ages, strengthening as pregnancy advances.