The frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes

OBJECTIVE: The purpose of this study was to determine the frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes. STUDY DESIGN: Amniotic fluid (AF) was retrieved from both sacs in 77 twin gestations with preterm labor and intact membranes (GA 35 weeks). Fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas and assayed for matrix metalloproteinase-8 (MMP-8). Intra-amniotic inflammation was defined as an elevated MMP-8 AF concentration ( 23 ng/mL). Non-parametric and survival techniques were used for analysis. RESULTS: 1) The rate of intra-amniotic inflammation (IAI) of at least one sac was 36% (28/77). Proven AF infection of at least one sac was detected in 12% (9/77), and IAI without proven AF infection was found in25%(19/77); 2) IAI was present in both sacs in 20 cases, in the presenting sac in 7 cases, and in the non-presenting sac in one case; 3) AF culture was positive in both sacs in 6 cases and in the presenting sac in 3 cases; 4) Patients with IAI of at least one sac and a negative AF culture had a significantly higher rate of adverse outcome than those with a negative AF culture and without IAI (a lower gestational age at birth, lower birth weight, shorter amniocentesis-to-delivery interval, histologic chorioamnionitis and significant neonatal morbidity). Importantly, there was no significant difference in pregnancy outcomes between patients with IAI and a negative culture and those with a positive AF culture. CONCLUSION: 1) IAI is present in 37% of twin pregnancies with preterm labor and intact membranes and is a risk factor for impending preterm delivery and adverse outcome. 2) IAI was found more frequently in the presenting sac than in the non-presenting sac, which supports the view that the ascending route is the common pathway of IAI.