screening of preterm labor in yazd city: transvaginal ultrasound assessment of the length of cervix in the second trimester

background: spontaneous preterm labor is one of the common obstetrics problems causing several physical, psychological and economical outcomes. although due to these outcomes and the efficacy of cares for decreasing them, preterm labor screening is cost-effective and it is still one of the challenging issues in obstetrics. objective: in this study preterm labor screening by using cervical transvaginal sonography was evaluated. materials and methods: this observational cohort study was performed in yazd, iran. samples were selected from pregnant women at gestational age of 21-24 weeks who had single live fetus and referred to the obstetrics clinics of two selected hospitals in yazd. gestational age was estimated based on the sonography of the first trimester and cervical length measured by transvaginal sonography. data analysis was done by using t and x2 test as well as anova. statistical significant level was considered as p<0.05. results: from 450 participants, 47 cases had preterm labor and 6 cases had positive funneling. mean age of women with term labor was 26.09±4.13 years and that of women with preterm labor was 26.7±3.51 years (p=0.334). duration of pregnancy and cervical length significantly differed between women with and without funneling (p=0.001). the sensitivity and specificity of screening based on cervical length of 25mm were 55.5% (50.9-60.1%) and 93.6% (91.2-96%) respectively. conclusion: based on the results of the present study, transvaginal ultrasound assessment of cervical length in low risk women has an acceptable reliability for screening of preterm labor.