Microbial invasion and cytokine response in amniotic fluid in a Swedish population of women in preterm labor

Background. Previous studies indicate an association between intra-amniotic microbial invasion and/or inflammation and spontaneous preterm birth, but there is a limited amount of data available from Europe. The aim of this study was to investigate the occurrence of intra-amniotic microorganisms and cytokines (interleukin-6 and interleukin-8) in a Swedish population of women in preterm labor and their correlation with preterm birth. Methods. Amniotic fluid was retrieved transabdominally from 61 patients in preterm labor before 34 weeks of gestation. Polymerase chain reaction analyses for Ureaplasma urealyticum and Mycoplasma hominis and culture for aerobic and anaerobic bacteria were performed. Interleukin-6 and interleukin-8 were analyzed with enzyme-linked immunosorbent assay. Results. Microorganisms in amniotic fluid were detected in 10 patients (16%). Patients with detected bacteria in the amniotic fluid had significantly higher levels of interleukin-6 and interleukin-8. There was also an association between interleukin-6/-8, the amniocentesis-delivery interval (less than or equal to 7 days) and preterm birth (<34 weeks). An amniotic fluid concentration of interleukin-6 greater than or equal to 1.5 ng/mL or interleukin-8 greater than or equal to 1.3 ng/mL was associated with an increased risk of delivery within 7 days (interleukin-6: relative risk 7.3; 95% confidence interval: 2.8-19; sensitivity 83%, specificity 87%; interleukin-8: relative risk 14, 95% confidence interval: 3.6-55, sensitivity 91%, specificity 87%). Conclusions. The occurrence of intra-amniotic microbial invasion and inflammation in this population of Swedish women in preterm labor was similar to data reported from populations with a higher incidence of preterm delivery. Amniotic interleukin-6 and interleukin-8 correlated with the presence of microorganisms and with preterm birth.