The cervix as a predictor of preterm delivery in 'at-risk' women

Objective To examine the relationship between ultrasound-determined cervica l status and pregnancy outcome in women 'at-risk' of spontaneous preterm de livery. Design A prospective cohort study of 120 pregnant women considered to be 'a t-risk' of spontaneous preterm delivery by their clinician. Transvaginal ul trasound of the cervix was used to assess overall cervical length, closed e ndocervical canal length, diameter and internal os dilatation in the second trimester. The main outcome measure was occurrence of spontaneous preterm birth (<34 and <37 weeks of gestation). Results The overall preterm delivery rate (< 37 weeks gestation) in these w omen was 35% (n = 42) with 20% (n = 24) delivering < 34 weeks gestation. Of the 71 women with a normal cervix, 8 (11%) delivered < 34 weeks, whereas o f the 49 women with an abnormal cervix, 16 (33%) delivered < 34 weeks (RR 2 .90; 95% CI 1.35-6.24). Using linear regression, closed endocervical canal length of < 21 mm before 20 weeks is associated with delivery < 34 weeks in 95% of women, and with delivery < 37 weeks in 95% of women if the canal le ngth is < 33 mm. Logistic regression showed closed endocervical canal lengt h to be the only significant factor in those women who delivered < 34 weeks after controlling for possible confounders. Conclusions A strong relationship is demonstrated between cervical status a nd pregnancy outcome, particularly the cervical findings before 20 and 24 w eeks of gestation. The length of the closed portion of the endocervical can al is the best predictor A beneficial effect of this approach to 'at-risk' women is the reduction in unnecessary interventions in those with normal ce rvical findings.