Amniotic fluid volume in intra-amniotic inflammation with and without culture-proven amniotic fluid infection in preterm premature rupture of membranes

Abstract

Previous studies reported that the clinical significance of intra-amniotic inflammation with a negative amniotic fluid (AF) culture is similar to that of intra-amniotic inflammation with microbiologically-proven AF infection. However, the magnitude of the fetal inflammatory response in these two conditions is different as gauged by umbilical cord C-reactive protein (CRP) concentrations. We undertook this study to determine if the frequency of oligohydramnios is different in these two conditions. The amniotic fluid index (AFI) was measured in 205 patients with preterm premature rupture of membranes (PROM) (<or=35 weeks). AF was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. Intra-amniotic inflammation was defined as an elevated AF matrix metalloproteinase-8 (MMP-8) concentration (>23 ng/mL). Patients were divided into three groups according to the results of AF culture and the presence or absence of intra-amniotic inflammation: 1) without intra-amniotic inflammation and a negative culture (n=109); 2) with intra-amniotic inflammation and a negative culture (n=44); and 3) a positive culture (n=52). Patients with a positive culture had a higher frequency of oligohydramnios and a lower median AFI than those with a negative culture but with intra-amniotic inflammation (P<0.01). However, there was no significant difference in the median AFI or in the frequency of oligo-hydramnios according to the presence or absence of intra-amniotic inflammation among patients with a negative culture (P>0.1). Oligohydramnios was more frequent in patients with culture-proven AF infection than in those with intra-amniotic inflammation and a negative AF culture.