How to identify twins at low risk of spontaneous preterm delivery
Article first published online: 22 JUL 2005
Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Ultrasound in Obstetrics & Gynecology
Volume 26, Issue 2, pages 138–144, August 2005
How to Cite
Sperling, L., Kiil, C., Larsen, L. U., Qvist, I., Bach, D., Wøjdemann, K., Bladh, A., Nikkilä, A., Jørgensen, C., Skajaa, K., Bang, J. and Tabor, A. (2005), How to identify twins at low risk of spontaneous preterm delivery. Ultrasound Obstet Gynecol, 26: 138–144. doi: 10.1002/uog.1938
- Issue published online: 22 JUL 2005
- Article first published online: 22 JUL 2005
- Manuscript Accepted: 22 APR 2005
- cervical assessment;
- multiple pregnancy;
- preterm delivery;
- twin pregnancy;
The aim of this study was to evaluate transvaginal sonographic assessment of cervical length at 23 weeks as a screening test for spontaneous preterm delivery in order to define a cut-off value that could be used to select twin pregnancies at low risk of spontaneous preterm delivery.
In a prospective multicenter study of 383 twin pregnancies included before 14 + 6 weeks a cervical scan with measurement of the cervical length was performed at 23 weeks' gestation. The results were blinded for the clinicians if the cervical length was ≥ 15 mm. The rates of spontaneous delivery at different cut-off levels of cervical length were determined.
Eighty-nine percent of the twins had dichorionic placentation and 58% were conceived after assisted reproduction. The rate of spontaneous preterm delivery was 2.3% (1.5% for dichorionic (DC) and 9.1% for (MC) monochorionic twins) before 28 weeks and 18.5% (17.1% for DC and 29.5% for MC twins) before 35 weeks. The screen-positive rate was 5% for a cervical length ≤ 20, 7–8% at ≤ 25, 16–17% at ≤ 30 and 34–48% at ≤ 35 mm depending on chorionicity. The false-negative rate (1 − negative predictive value) ranged from 1.2% at 28 weeks to 18.6% at 35 weeks for all twins. Receiver–operating characteristics curves showed that the sensitivity increased with declining gestational age with cut-off levels of highest accuracy at 21 mm for 28 weeks and 29 mm for 33 weeks.
Cervical length measurement at 23 weeks of gestation is a good screening test for predicting twins at low risk of preterm and very preterm delivery, especially in DC twins. The present results suggest that a cut-off of 25 mm should be recommended. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.