Cervical funneling: sonographic criteria predictive of preterm delivery

Our objective was to establish sonographic criteria that are predictive of preterm in delivery in patients with internal os dilatation (funneling). The study population consisted of patients with cervical funneling identified on translabial or transvaginal ultrasound examination. Funnel length, functional length, percentage funneling and funnel width were evaluated for their predictive values for preterm delivery. In the 43 patients who met the study criteria, funneling was detected at a mean gestational age of 21.4 weeks (range 16-28). Twenty-three of 31 patients (74%), manually examined immediately following the ultrasound examination, had a closed cervix. Preterm delivery occurred in 42% of patients. Funnel length of greater than or equal to 16 mm, functional length of less than or equal to 20 mm, funneling of greater than or equal to 40% and funnel width of greater than or equal to 14 mm correlated significantly with preterm delivery. Patients with funneling of < 25%, 25-50% and > 50% had preterm delivery rates of 17%, 29% and 79%, respectively.