Prediction of preterm delivery with transvaginal ultrasonography of the cervix in patients with high-risk pregnancies: does cerclage prevent prematurity? - Berghella,V.; Daly,S.F.; Tolosa,J.E.; DiVito,M.M.; Chalmers,R.; Garg,N.; Bhullar,A.; Wapner,R.J. (Am J Obstet Gynecol, 1999)