Introduction: Chromosomal disorders are caused by changes occurring in either chromosome number or structure usually during the formation of gametes or soon after fertilisation. These changes can affect the autosomes, with chromosomal disorders divided into the two corresponding groups. Aims: To screen for chromosomal abnormalities namely trisomy 21, 18 & 13, during the first trimester of pregnancy using biochemical tests like freeβ-hCG, PAPP-A and ultra sound measurements of nuchal translucency, nasal bone and ductus venosus flow. Materials and methods:The Prospective study on early detection of chromosomal anomalies by performing a combination of biochemical and sonological tests between 11-14 wk of gestation. To the existing first trimester screening tests of double marker ( free β- hCG and PAPP-A) Combined with NT,two more sonological markers were added is NB,DVF to improve the diagnostic sensitivity