The first trimester screening programme offers a noninvasive option for the early detection of aneuploidy pregnancies. This screening is done by a combination of two biochemical markers i.e. serum free b-human chorionic gonadotrophin (free b-hCG) and pregnancy associated plasma protein A (PAPP-A), maternal age and fetal nuchal translucency (NT) thickness at 11 ? 0-13 ? 6 weeks of gestation. A beneficial consequence of screening is the early diagnosis or trisomies 21, 18 and 13. At 11 ? 0-13 ? 6 weeks, the relative prevalence of trisomies 18 and 13 to trisomy 21 are found to be one to three and one to seven, respectively. All three trisomies are associated with increased maternal age, increased fetal NT and decreased PAPP-A, but in trisomy 21 serum free b-hCG is increased whereas in trisomies 18 and 13 free b-hCG is decreased.Prenatal screening for trisomies based on the analysis of biochemical markers in maternal serum has become an established part of obstetric practice in many countries. Resent interest in prenatal screening for trisomies has focused on the first trimester. Of the biochemical markers that have been investigated, only maternal serum free b-human chorionic gonadotrophin (free b-hCG) and pregnancy associated plasma protein-A (PAPP-A) has been shown to be of value. The goal of first trimester maternal serum screening programs is to identify women at increased risk of having a baby affected with Down syndrome, Patau syndrome, and Edward syndrome defects and those that will benefit from the testing.The association between advancing maternal age [1] and increased risk of trisomy 21 (Table 1) is well known, and pregnant women older than 35 years at delivery are routinely offered invasive prenatal diagnostic testing. The most commonly used test for genetic diagnosis is amniocentesis, but the rate of spontaneous fetal loss related to amniocentesis averages about one in every 200 [2] procedures. Because of this risk, serum analyte testing has become an important, noninvasive first step in detecting patients at risk for congenital abnormalities.Current studies done on first trimester maternal serum screening has shown that the double marker test helps to identify 90 % of women at risk for Down syndrome, 94 % of all major chromosomal defects such as Patau syndrome, Edward syndrome, triploidy and Turner syndrome, and 60 % of other chromosomal defects, such as deletions, partial trisomies, unbalanced translocations, and sex chromosome aneuploidies other than turners [3]. Some of the advantages of first-trimester biochemical screening over second trimester biochemical screening include providing clinicians and patients with the substantial advantage of an earlier diagnosis, higher detection rates for fetal Down syndrome i.e; 90 % [4] or even higher, compared to 80 % for the second trimester quadruple test [5,6] and 70 % for the older triple screening test [7], and detection of most major chromosome abnormalities other than trisomy 21. It also acts as a nonspecific marker for other birth defects inclu...