Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high-risk pregnancies?
OBJECTIVE
To determine whether high-risk patients manifest cervical length < 25 mm on transvaginal ultrasound before 14 weeks of gestation, and if this finding is predictive of preterm delivery.


METHODS
Asymptomatic pregnancies at high risk for preterm birth were followed prospectively from 10 + 0 weeks to 13 + 6 weeks with transvaginal sonographic measurement of the cervix. A cervical length < 25 mm was considered a short cervix at this gestational age and at the follow-up ultrasound examinations, performed between 14 and 24 weeks. The primary outcome was preterm birth at < 35 weeks of gestation.


RESULTS
One hundred and eighty-three pregnancies met the study criteria and were included in the analysis. Only 10 (5%) patients had a cervix < 25 mm before 14 weeks. The sensitivity, specificity and positive and negative predictive values of a short cervix were 14%, 97%, 50%, and 82%, respectively (relative risk, 2.8; 95% confidence interval, 1.4-5.6). The mean transvaginal sonographic cervical length before 14 weeks of gestation was 33.7 +/- 6.9 mm in pregnancies which delivered preterm (n = 36), and 35.0 +/- 6.8 mm in those delivering at term (n = 147) (P = 0.3). Follow-up transvaginal ultrasound examination of the cervix to 24 weeks revealed that the average gestational age at which a short cervix was detected was 18.7 +/- 2.9 weeks.


CONCLUSIONS
A cervical length < 25 mm on transvaginal sonographic assessment rarely occurs before 14 weeks even in high-risk patients destined to deliver preterm; in these patients cervical changes predictive of preterm birth develop mostly after this gestational age.
Berghella
V
V
Division of Maternal Fetal Medicine, Department of Obstetrics & Gynecology, Jefferson Medical College of Thomas Jefferson University, Philadelphia 19107, USA. vincenzo.berghella@mail.tju.edu
Talucci
M
M
Desai
A
A
D000328:Adult; D002584:Cervix Uteri / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D018566:Pregnancy, High-Risk; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography