First-trimester screening for trisomy 21 in twin pregnancy: does the addition of biochemistry make an improvement?
Article first published online: 18 OCT 2005
Copyright © 2005 John Wiley & Sons, Ltd.
Volume 25, Issue 12, pages 1156–1161, 15 December 2005
How to Cite
Goncé, A., Borrell, A., Fortuny, A., Casals, E., Martínez, M. A., Mercadé, I., Cararach, V. and Vanrell, J. A. (2005), First-trimester screening for trisomy 21 in twin pregnancy: does the addition of biochemistry make an improvement?. Prenat. Diagn., 25: 1156–1161. doi: 10.1002/pd.1304
- Issue published online: 28 NOV 2005
- Article first published online: 18 OCT 2005
- Manuscript Accepted: 16 AUG 2005
- Manuscript Received: 27 JUL 2005
- Manuscript Revised: 27 JUL 2005
- first-trimester screening;
- trisomy 21;
- nuchal translucency;
- Combined Test
To evaluate the effectiveness of the addition of first-trimester biochemistry to fetal nuchal translucency (NT) measurement in the Combined Test when screening for trisomy 21 in twin pregnancies.
Maternal serum free β-hCG and PAPP-A were determined at 8 to 12 weeks and fetal NT was measured at 11 to 14 weeks. The individual risks were estimated for each of the fetuses using both NT screening alone and the Combined Test. An invasive diagnostic procedure was offered when the risk was 1:250 or over in either one of the fetuses. In the first period, only the results of NT screening were clinically applied. After previous analysis, the Combined Test was introduced into clinical practice.
In the two-and-a-half-year study period, a complete follow-up was obtained in 100 twin pregnancies. Three fetuses (two pregnancies) with trisomy 21 were detected by both methods. The false-positive rate achieved by NT screening (14.3% of pregnancies and 8.6% of fetuses) was substantially reduced when first-trimester biochemistry was added in the Combined Test (5.1% of pregnancies and 3.6% of fetuses).
The Combined Test appears to maintain the detection rate achieved by NT screening for trisomy 21 in twin pregnancies, but false-positive rates and invasive diagnostic procedures are reduced. Copyright © 2005 John Wiley & Sons, Ltd.