Preterm delivery and ultrasound measurement of cervical length in Gran Canaria, Spain

OBJECTIVE: To study the relationship between cervical length measured by ultrasound and risk of preterm delivery. METHODS: We measured cervical length in 2351 women between the 18th and 22nd week of pregnancy. Preterm delivery was categorized as before 37 weeks, before 34 weeks, and before 30 weeks. RESULTS: Before the 37th week, the odds ratios (ORs) of spontaneous delivery for cervical lengths in the 3rd, 5th, and 10th percentiles were, respectively, 25.47 (95% confidence intervals [CI], 15.5-41.73); 16.98 (95% CI, 11.51-25.05); and 7.55 (95% CI, 5.44-10.5). Before the 34th week the ORs were 28.7 (95% CI, 14.54-41.73); 20.5 (95% CI, 11.51-25.05); and 10.3 (95% CI, 5.44-10.5). And before the 30th week they were 29.8 (95% CI, 15.54-41.73); 23.1 (95% CI, 11.51-25.05); and 19.1 (95% CI, 7.44-31.5). In predicting premature delivery, the sensitivity, specificity, positive predictive value, and negative predictive value of cervical length were 26%, 98%, 63.6%, and 93.57% for the 3rd percentile; 34%, 97%, 51%, and 94% for the 5th percentile; and 39%, 92%, 31%, and 94% for the 10th percentile. CONCLUSION: Transvaginal measurement of cervical length during routine fetal morphological examination between the 18th and 22nd week of pregnancy helps identify asymptomatic women at risk for preterm delivery.