Second trimester ultrasound prenasal thickness combined with nasal bone length: a new method of Down syndrome screening.

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.

Comparison between disclosure and non-disclosure approaches for trisomy 21 screening tests.

Background: First-trimester nuchal translucency (NT) and second-trimester triple test (TT) are common screening programmes for trisomy 21. The aim of this study was to compare disclosure and non-disclosure approaches of combining those tests.

Methods: Likelihood ratios of both NT and TT tests, among 508 normal and 23 trisomy 21-affected pregnancies, were used for calculating population-adjusted risks.