OBJECTIVE:The aim of this study was to estimate the probability of spontaneous delivery at 34 weeks or less according to cervical assessment by transvaginal scan associated with previous obstetric history. METHODS: Ultrasound transvaginal cervical length and presence of funneling were evaluated in 1,958 singleton pregnancies between 21 and 24 weeks of gestation. For the prediction of preterm delivery, the results of cervical assessment were analyzed in association with the previous obstetric history of preterm delivery, spontaneous miscarriage, and curettage. Sensitivity, specificity, and positive and negative predictive values for the various cutoff cervical lengths in the groups with or without previous history of preterm delivery were calculated. Multivariable regression analysis was used to identify the predictive factors for preterm delivery at 34 weeks or less. RESULTS: The incidence of spontaneous delivery at gestational age of 34 weeks or less was 3.4%. The mean cervical length was 30.1 mm (standard deviation 10.1 mm) in the group with previous history of prematurity (a = 180) and 35.8 mm (standard deviation 7.9 mm) in the group without previous history of prematurity (P <.001). The mean cervical length in the group of patients who delivered at or before 34 weeks was 23.8 mm, and for patients who delivered after 34 weeks it was 35.6 mm (P < .001). The mean gestational age at delivery was significantly lower in the group with funneling compared with the group without funneling (33.5 weeks versus 38.8 weeks, P < .001). Logistic regression analysis demonstrated that cervical length, funneling, and history of previous preterm delivery were independent contributors for preterm delivery. CONCLUSION: Ultrasound cervical assessment may be useful in the prediction of preterm delivery, but it should also be considered in association with the obstetric history of prematurity. OBJECTIVE: The aim of this study was to estimate the probability of spontaneous delivery at 34 weeks or less according to cervical assessment by transvaginal scan associated with previous obstetric history. METHODS: Ultrasound transvaginal cervical length and presence of funneling were evaluated in 1,958 singleton pregnancies between For the prediction of preterm delivery, the results of cervical assessment were analyzed in association with the previous obstetric history of preterm delivery, spontaneous miscarriage, and curettage. Sensitivity, specificity, and positive and negative predictive values ​​for the various cutoff cervical lengths in the groups with or without previous history of preterm delivery were calculated. Multivariable regression analysis was used to identify the predictive factors for preterm delivery at 34 weeks or less. RESULTS: The incidence of spontaneous delivery at gestational age of 34 weeks or less was 3.4%. The mean cervical length was 30.1 mm (standard deviation 10.1 mm) in the group with previous history of prematurity (a = 180) and 35.8 mm (standard deviation 7.9 mm) in the group without previous history of prematurity (P <.001). The mean cervical length in the group of patients who delivered at or before 34 weeks was 23.8 mm, and for patients who delivered after 34 weeks it was 35.6 mm (P <.001). The mean gestational age at delivery was significantly lower in the group with funneling than with the group without funneling (33.5 weeks versus 38.8 weeks, P <.001). Logistic regression analysis demonstrated that cervical length, funneling, and history of previous preterm delivery were independent contributors for preterm delivery. CONCLUSION: Ultrasound cervical assessment may be useful in the prediction of preterm delivery, but it it should also be considered in association with the obstetric history of prematurity.