Screening for trisomies in dichorionic twins by measurement of fetal nuchal translucency thickness according to the mixture model
Article first published online: 5 JAN 2011
Copyright © 2011 John Wiley & Sons, Ltd.
Special Issue: 1st Trimester Screening and Diagnosis
Volume 31, Issue 1, pages 16–21, January 2011
How to Cite
Wright, D., Syngelaki, A., Staboulidou, I., Jesus Cruz, J. d. and Nicolaides, K. H. (2011), Screening for trisomies in dichorionic twins by measurement of fetal nuchal translucency thickness according to the mixture model. Prenat. Diagn., 31: 16–21. doi: 10.1002/pd.2643
- Issue published online: 5 JAN 2011
- Article first published online: 5 JAN 2011
- Manuscript Revised: 6 SEP 2010
- Manuscript Accepted: 6 SEP 2010
- Manuscript Received: 18 AUG 2010
- first-trimester screening;
- trisomy 21;
- trisomy 18;
- trisomy 13;
- dichorionic twins;
- nuchal translucency
To examine the distribution of fetal nuchal translucency (NT) thickness in dichorionic twins and investigate the effect of the correlation between NT measurements in each twin pair on the performance of screening for trisomies.
The distribution of fetal NT for crown–rump length (CRL) was examined in 5646 dichorionic twin pregnancies, including 103 with fetal trisomies 21, 18 or 13. The correlation in fetal NT in each euploid twin pregnancy was estimated.
The distribution of NT in both euploid and trisomic fetuses was consistent with the mixture model in singleton pregnancies. In the euploid pregnancies, there was a correlation in log NT measurements in each twin pair (r = 0.42, 95% CI: 0.39–0.45) and, after removal of the effect of the operator, this correlation was reduced to 0.34. Allowing for this correlation in risk assessment for trisomies had a major impact on the estimated patient-specific risk but had little effect on the overall performance of screening.
In dichorionic twin pregnancies, the mixture model of distributions of NT can be applied as in singletons. In screening for trisomies, the correlation in NT measurements between the fetuses should be taken into account in the estimation of patient-specific risks. Copyright © 2011 John Wiley & Sons, Ltd.