Antenatal screening is the identification of women who are at increased risk of having a pregnancy affected by serous fetal abnormalities. Routine antenatal screening for Down syndrome is now established practice in most obstetric units. This article reviews the various methods of screening for Down syndrome aiming the detection of ideal screening test. That is provide appropriate information and personal support helping the family to make decision that feel are right for them.Maternal age is the first marker for antenatal screening of Down syndrome. Then, both the biochemical and ultrasound markers play an important role in screening for Down syndrome. The screening test may be done in the first or second trimester. The first trimester maternal serum screening markers, pregnancy associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotrophin (β-hCG), are useful for identifying women at increased risk for fetal Down syndrome. In addition, measurement of nuchal translucency has been demonstrated to be an indicator for these high-risk pregnancies. The second trimester serum screening involves combining the maternal age-specific risk for an affected pregnancy with the risks associated with the concentrations of maternal serum alpha-fetoprotein (MSAFP), unconjugated oestriol (uE3) and human chorionic gonadotrophin (hCG) to form the triple test.