Cervical length in women in preterm labor with intact membranes: Relationship to intra-amniotic inflammation/microbial invasion, cervical inflammation and preterm delivery

Abstract

Objective: Intra-amniotic infection, diagnosed by microbial invasion of the amniotic cavity (MIAC) and/or the presence of intra-amniotic inflammation (IAI), is related to adverse perinatal outcome in women with preterm labor. Due to the subclinical nature of IAI, a correct diagnosis depends on amniocentesis, which is an invasive method not performed as a clinical routine. The aim of this study was to evaluate if cervical length measured by transvaginal sonography could assist in the identification of women at high risk for IAI. Methods: Cervical length was assessed by transvaginal sonography in 87 women with singleton pregnancies in preterm labor (< 34 weeks of gestation). Cervical (n = 87) and amniotic (n = 55) fluids were collected. Polymerase chain reactions for Ureaplasma urealyticum and Mycoplasma hominis, and culture for aerobic and anaerobic bacteria, were performed. Interleukin (IL)-6 and IL-8 were analyzed by enzyme-linked immunosorbent assay. Results: IAI was present in 25/55 (45%) of the patients presenting with preterm labor who underwent amniocentesis. Women with IAI had a significantly shorter cervical length (median, 10 (range, 0-34) mm) than had those without IAI (median, 21 (range, 11-43) mm) (P < 0.0001). Receiver-operating characteristics curve analysis showed that a cervical length (cut-off of 15 mm) predicted IAI (relative risk, 3.6; CI, 1.9-10.0) with a sensitivity of 72%, specificity of 83%, positive predictive value of 78% and negative predictive value of 78%. Cervical length was also significantly associated with preterm birth up to 7 days from sampling and at ≤ 34 weeks. Conclusion: Cervical length assessed by transvaginal sonography predicts IAI as well as preterm birth and could thereby be a useful clinical tool in the management of patients in preterm labor. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.