Histologic chorioamnionitis & its association with prematurity in a hospital-based study

This prospective study was undertaken to study the occurrence of histologic chorioamnionitis and determine its association with prematurity; and to assess whether colonization of the genital tract of pregnant women by genital mycoplasmas or Chlamydia trachomatis is a risk factor for histologic chorioamnionitis. A total of 268 women with singleton pregnancies of over 26 weeks gestation were subjected to high vaginal cultures of genital mycoplasmas and endocervical specimens for chlamydia antigen. Placental histopathology was performed on multiple sections. Histologic chorioamnionitis was documented in 22.4 per cent (60/208) placentae. Genital tract colonization with Ureaplasma urealyticum or C. trachomatis was not a risk factor for histologic chorioamnionitis. Neonates born in association with histologic chorioamnionitis had a mean birth weight 111 g lower than those born without this lesion (2626.9 +/- 702 g vs 2737.8 +/- 500 g, NS). The relative risk (95% confidence interval) of prematurity in the presence of histologic chorioamnionitis was 1.49 (0.87-2.53). Analysis of linear trend in proportions for prevalence of histologic chorioamnionitis with decreasing gestation showed a significant association (P = 0.047, 1-tail). These results taken together suggest that histologic chorioamnionitis may be a risk factor of prematurity, but of only a modest magnitude.