ObjectiveTo study the value of plasma corticotropin-releasing hormone (CRH) and the fetal fibronectin (fFN) in vaginal secretions and cervical length in predicting preterm labor.MethodsThe plasma CRH levels and fFN levels in vaginal secretions from 24 -37 weeks pregnant woman checked up in our hospital from Dec.2009 to Dec.2010 were detected by ELLISA method.The changes of these three indexes were observed with the pregnant time and were analyzed according to different pregnancy outcomes.Results Among the 112 cases of pregnant women,premature delivery in 54 cases,full-term birth 58 cases.At the 24 week of pregnancy,there were significant difference on the cervical length( [2.8 ±0.4]cm vs [3.3 ±0.5]cm,t =3.254,P =0.021 ) between premature delivery group and full-term birth group.At the 28 - 30 week,31 -32 week,33 - 34 week,35 - 36 week,the CRH were ( 162.33 ± 16.49 ) ng/L,(60.01:±: 14.56) ng/L;(352.12 ±61.01 )ng/L,( 118.04 ±53.74)ng/L; (364.55 ±56.71 )ng/L,( 122.95 ±71.41 )ng/L; (372.78 ±149.89)ng/L,(124.00 ± 19.05 )ng/L respectively in premature delivery group and full-term birth group,and there were significant differences on CRH at the four different pregnant time(t =3.687,6.875,8.652,8.524,respectively,P ＜ 0.05 ).It shows better sensitivity ( 97.92％ ),specificity ( 90.00％ ),positive predictive value(95.92％ ) and negative predictive value(94.73％ ) in predicting premature delivery by detection of CRH,fFN combined with cervical length.ConclusionDetection of plasma CRH,fFN combined with cervix length measurement can improve the predictability of premature and provide a good,reliable clinical basis for the early diagnosis and treatment for preterm premature.