5Morteza T. Measurement of cervical length changes during normal pregnancy by endovaginal ultrasound device [ J ]. Iranian Journal of Radiology, 2011,6 ( S 1 ).
6Harika B, Arda L, Cem D, et al. The impact of cervical dilatation on pregnancy outcomes after cerclage placement in women with a short cervical length [ J ]. Journal of the Turkish - German Gynecological As- sociation ,2010,11 ( ! ). DOI.
7Ventura W,Huaman-Guerrero M.Comment on"what is predictive of preterm delivery in the first trimester:isthmus or cervical length?"[J].Prenat Diagn,2013,33(13):1321.
8Portela SN,Rocha-De-Souza R,Oppermann-Lisboa K,et al.Maternal physical activity,cervical length and its relation to spontaneous vaginal birth at term[J].Arch Gynecol Obstet,2014,290(2):257-262.
9Parry S,Elovitz MA.Pros and cons of maternal cervical length screening to identify women at risk of spontaneous preterm delivery[J].Clin Obstet Gynecol,2014,57(3):537-546.
10Moroz LA,Simhan HN.Rate of sonographic cervical shortening and biologic pathways of spontaneous preterm birth[J].Am J Obstet Gynecol,2014,210(6):555.e1-5.