The purpose of this study was to evaluate first trimester biochemical screening benefit with and without adding NT in enlarged measurements on screening performances. Methods: Nine thousands five hundreds and twenty-three patients underwent first trimester screening performing NT measurement and first trimester serum screening. Clinical management was decided on the basis of NT/biochemistry risk calculation. Retrospectively enlarged NT were evaluated and risk calculation was evaluated with and without NT measurements when above 2.0 MoM. Results: One hundred and seven fetuses presented at 11-14 weeks' gestation NT measurement above 2.0 MoM. 87 presented positive ultrasound-biochemical screening whilst only 21 had a positive risk calculation using only PAPP-A and free beta hCG. 24 patients were lost at follow-up. The whole population with adverse obstetric outcome (27 patients) where within the 87 with combined screen positive (Detection rate 100%; 87-100% CI 95%), while only nine were detected by biochemical screen (Detection rate 33%; 17-54% CI 95%). Seven cases of trisomy 21 were identified by combined screen (Detection rate 100%; 59-100% CI 95%) and only five by biochemistry alone (detection rate 71%; 29-96% CI 95%). Conclusions: NT measurements above 2.0 MoM increase significantly the risk from biochemistry having 4 times positive screen patients. Whilst an increase of OAPR, the detection rate is reduced significantly not considering NT measurements above 2.0 MoM. Larger population is needed in order to confirm our population result and screening policy.