Prediction of time of delivery using cervical length measurement in women with threatened preterm labor.

OBJECTIVE

To evaluate the use of transvaginal (TV) sonographic cervical length (CL) measurement alone in predicting time of delivery in women who present in threatened preterm labor.

METHODS

A retrospective cohort study at Royal Brisbane and Women's Hospital of all women who presented between 22 weeks and 0 days and 35 weeks and six-day gestation in threatened preterm labor and were admitted for ongoing management including a TV sonographic CL measure. The accuracy of CL for predicting time of delivery was compared between women with a short cervix (CL  < 25 mm) and those with a normal cervix (CL ≥25 mm). The predictive accuracy of CL for spontaneous preterm delivery was analyzed with different outcome-specific thresholds.

RESULTS

One hundred and forty-six women with threatened preterm labor met the inclusion criteria; of which 74 (50.7%) had a short cervix and 72 (49.3%) had a normal cervix. The group with short cervix were more likely to deliver prematurely before 37-week gestation, as well as a shorter time interval between initial presentation and delivery and delivery within 14 days from presentation ( = .0002,  = .0001, and  = .0001, respectively). Similarly, with respect to the area under the receiver operator characteristic curves, CL measurement was found to be significant for time of delivery before or after 37 weeks ( < .0001), preterm delivery before 34 ( =  .0003) and 31 ( <  .0001) weeks; and preterm delivery within 14 days from presentation ( < .0001). Cervical length measurement has a high negative predictive value ranging from 94.9 to 97.1% depending on the different CL threshold used.

CONCLUSIONS

Cervical length measurement at the time of presentation was significantly associated with the risk of preterm delivery in women presenting with threatened preterm labor and a short cervix. Cervical length measurement was also helpful in predicting time of delivery within 14 days from presentation. The negative predictive value and predictive accuracy of CL as a single measure were of significance.