First trimester ultrasound with nuchal translucency measurement for Down syndrome risk estimation using software developed by the Fetal Medicine Foundation, United Kingdom--the first 2000 examinations in Newcastle, New South Wales, Australia.

In September 1997 screening for Down syndrome using first trimester ultrasound to measure nuchal translucency, with risk estimation by the software program developed in the United Kingdom by the Fetal Medicine Foundation, was introduced in Newcastle, New South Wales. In the first 2,000 such risk estimations 134 women (6.7 %) were screen positive (with a risk of greater than 1 in 300 at that gestation for Trisomy 21). In the first 1,000 of these 2,000 fetuses delivered thus far there were 8 cases of Trisomy 21, 2 of Trisomy 18 and 1 of 47 XXX. Nine of these 11 were screen positive, the only false negative results being for 2 cases of Trisomy 21. The detection rate for Trisomy 21 was 6 out of 8 (75%) and for every case of Trisomy 21 (Down Syndrome) detected by this process, 11.3 invasive tests would have been needed to make that diagnosis in a screen positive woman.