FIRST TRIMESTER ANEUPLOIDY SCREENING USING NUCHAL TRANSLUCENCY, FREE BETA-HUMAN CHORIONIC-GONADOTROPIN AND MATERNAL AGE

Screening for aneuploidy using maternal age has a low detection rate a nd high false positive rate. Second trimester maternal serum screening increases trisomy 21 detection and decreases the false positive rate. First trimester screening would enable definitive diagnosis with chor ionic villus sampling, and simple surgical termination of affected pre gnancies would still be an option. Nuchal translucency (NT), free beta human chorionic gonadotrophin (f beta HCG) and maternal age were asse ssed in 302 patients before chorionic villus sampling. NT positively a nd f beta HCG negatively correlated with gestation, but neither correl ated with maternal age nor with each other. Both NT and f beta HCG wer e increased in trisomy 21. NT was increased and f beta HCG was decreas ed in trisomy 18, Multivariate discriminant analysis enabled 87.5% det ection of trisomy 21 in this high-risk population, for a 14% false pos itive rate, In a simulated normal population, using a risk cut-off of 1 in 250, 71% detection was achieved for a 7% false positive rate. The combination of NT, f beta HCG and maternal age is a simple, readily a vailable and viable first trimester screening strategy.