Premium
Second trimester ultrasound prenasal thickness combined with nasal bone length: a new method of Down syndrome screening
Author(s) -
Maymon Ron,
LevinsohnTavor Orna,
Cuckle Howard,
Tovbin Yosef,
Dreazen Eli,
Wiener Yifat,
Herman Arie
Publication year - 2005
Publication title -
prenatal diagnosis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.956
H-Index - 97
eISSN - 1097-0223
pISSN - 0197-3851
DOI - 10.1002/pd.1207
Subject(s) - nasal bone , medicine , fetus , down syndrome , ultrasound , gestation , wilcoxon signed rank test , nuclear medicine , prenatal screening , prenatal diagnosis , pregnancy , anatomy , radiology , biology , mann–whitney u test , psychiatry , genetics
Objective To evaluate ultrasound prenasal thickness (PT) as a way of enhancing the Down syndrome (DS) screening performance of second‐trimester nasal bone (NB) length measurement. Methods Twenty‐one DS and 500 normal fetuses were scanned at 14–27 weeks' gestation. The affected karyotype was known to the person performing the scan. Both PT and NB were measured in a mid‐sagittal position and results were expressed in multiples of the normal gestation‐specific median (MoM). Gaussian modelling was used to predict the performance of routine screening. Results Among DS fetuses, the PT median was 1.35 MoM, a highly statistically significant increase compared with the unaffected pregnancies ( p < 0.0001, Wilcoxon Rank Sum Test, two‐tailed). The NB median was 0.87 MoM ( p < 0.0005) and the ratio PT/NB median was 1.51 MoM ( p < 0.0001). In the normal fetuses, the two markers were positively correlated (0.25, p < 0.0001), whereas in the DS fetuses there was a non‐significant negative correlation (−0.24, p = 0.33). For a 5% false‐positive rate, the model predicted detection rate was 70% for PT and NB compared with 43% for NB alone. Conclusion In the second trimester, PT is increased on average in DS fetuses. Combining PT and NB measurement could yield a higher screening detection rate than NB alone. Confirmation of our findings in a series of women scanned before the karyotype was known is needed before the method can be clinically implemented. Copyright © 2005 John Wiley & Sons, Ltd.