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

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 <or=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.