Cervical length and dilatation of the internal cervical os detected by vaginal ultrasonography as markers for preterm delivery: A systematic review

OBJECTIVE: We performed a systematic review to evaluate endovaginal cervical ultrasonography as a predictor of preterm delivery. STUDY DESIGN: Selection criteria were original published English-language reports of prospective studies including women at <37 weeks' gestation with intact amniotic membranes Parameters and outcomes were cervical-length or dilatation of the internal cervical os and preterm delivery. RESULTS: In 3 subgroups of studies including patients with preterm labor or low-risk, symptom-free patients with early (20-24 weeks) or late (27-32 weeks) ultrasonographic examination, optimal cutoff values for cervical lengths ranged between 18 and 30, 25 and 35, or 25 and 39 mm. At these Cutoff values, sensitivity rates were:between 68% and 100%, 33% and 54%, or 63% and 76%, and specificity-rates were between 44% and 79%, 73% and 91%, or 59% and 69%, respectively. Sensitivity rates for dilatation of the internal cervical os were 76% to 100%, 16% to 25%, or 33%, and specificity rates were 54% to 75%, 95% to 99%, or 92%, respectively. CONCLUSION: In patients with symptoms of preterm labor, endovaginal cervical ultrasonography appears to be an effective predictor of preterm delivery.