The Dual Screen test between 9-13 weeks of pregnancy has significant utility in First trimester Prenatal Screening of Down Syndrome (Trisomy 21), and other chromosomal anomalies. The false positive rate is 5-7 % but the detection of Down Syndrome is as high as 85-90%.The dual marker test is done to analyzes the certain genetic disorder in an unborn baby at 10 - 13 weeks of pregnancy. It is also known as a multiple marker test. The test measures the levels of two important hormones in the placenta. Abnormal levels of these substances may indicate the presence of: Down syndrome neural tube defects (such as spina bifida and anencephaly). multiple infants(Free-beta hCG & PAPPA)*Risk (Valid between 9-13 weeks gestation - Ideal 10-13 weeks)