Cervical Interleukin-6 as a Predictive Test for Preterm Delivery in Symptomatic Women: Preliminary Results

The outcome for babies delivered after 34 weeks' gestation is generally good, but deliveries at extreme prematurity between 24 and 32 weeks are at high risk of complications. Previous studies investigating risk factors predictive for premature delivery have demonstrated a clear association between ultrasonographic cervical length and preterm delivery. Another possible preterm delivery predictive risk factor is the concentration of cervical interleukin-6 (IL-6). Through increased production of prostaglandins, this cytokine seems to be involved in events leading to cervical ripening and uterine contractions. This observational prospective study was designed to investigate cervical IL-6 presence and concentrations for preterm delivery, alone and in association with cervical length as a predictive diagnostic test for preterm delivery in high-risk symptomatic women. The study subjects were 100 women between 24 and 34 weeks of gestation with intact membranes but threatened preterm labor who had been admitted to a hospital in Spain from 2006 to 2008. Cervical fluid was analyzed with transvaginal scan to determine cervical length, and a cervical swab was taken for detection of IL-6. Statistical tests performed included χ2 test, Cox and logistic regression, receiver operating characteristic curve analysis, and Kaplan-Meier survival analysis. Preterm delivery occurred in 35% of the babies born before 37 weeks and in 5% before 32 weeks. Cervical length was <15 mm in 12% and <30 mm in 62% of the subjects. Receiver operating characteristic curve analysis showed that an IL-6 value >210 pg/mL and a cervical length <30 mm were useful predictors of preterm delivery within 48 hours, within 7 days, and at <32, <34, and <37 weeks; there was no difference between the predictive accuracy of IL-6 and cervical length. Their additive predictive value was greater than either alone. These findings suggest that cervical IL-6 and cervical length are predictive risk factors for preterm delivery in symptomatic women at high risk and that when combined, the predictive accuracy of both is better than each test alone.