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Down syndrome is the most common individual cause of mental retardation in children. Prenatal screening for Down syndrome, based on the maternal age, has been practised in Slovenia since 1981. Between 1987 and 1994, Down syndrome was diagnosed prenatally in merely 17% of infants. In 1995, triple-marker testing for the second trimester prenatal diag­nosis of Down syndrome was introduced. Using this method we measured alpha-fetoprotein, human chorionic gonadotrophin and unconju­gated estriol in maternal blood, and estimated the pregnant woman’s risk of carrying a baby with Down syndrome. The expected percentage of detected Down syndrome cases is approxi­mately 60%, with the rate of false positive results being 5 to 7%. The paper describes some practical aspects of the test, and pre­sents pregnancy complications after a false-pos­itive screen for Down syndrome. The paper describes a screening method using ultrasound measurements of fetal nuchal translucency, and new laboratory tests, likely to become useful tools of prenatal diagnosis of Down syndrome in the future.