Screening means looking for disease in a population in individuals without signs or symptoms of that disease. Unlike most medicine, in screening, tests are performed without any clinical indication of disease. Screening is done where the condition is identified as an important health problem, facilities for diagnosis and treatment are available, and the test is acceptable to the population. In the first trimester, screening is carried out for: (a) Chromosomal defects (mainly Trisomy 21, that being the commonest chromosomal anomaly but also Trisomy 18 and 13), (b) Major fetal abnormalities, (c) Twin pregnancies—screening for chromosomal abnormalities and the determination of chorionicity, (d) Pre-eclampsia. To screen for and to detect congenital anomalies is one of the primary goals of prenatal surveillance. Accurate prenatal diagnosis and timely termination of the cases complicated by serious fetal malformations leads to a marked reduction in perinatal morbidity and mortality. The sensitivity for anomalies detection varies considerably depending on the operator expertise, gestational age at examination and the equipment resolution. The optimal time to scan for most developmental anomalies is 18-22 weeks. The message is that a little color sheds more light but color alone isn’t enough and today we are observing a colorful revolution of monumental proportions in the field of obstetrics. The genetic sonogram is an ultrasound examination done on second trimester fetuses to not only evaluate the fetus for structural malformations, but also search for ultrasound markers of fetal Down’s syndrome. Most workers have extended the definition to the second trimester fetal anatomic survey targeted at identifying features associated with any aneuploidy. It has evolved as an adjunctive screening tool capable of further refining the individualized risk-calculation for trisomy that is based on maternal age or serum screening markers and identifies pregnancies where invasive testing for a fetal karyotype should be encouraged.