It is now clear that the vast majority of major fetal abnormalities can be diagnosed prenatally by ultrasound, that most of these abnormalities can be detected in the first trimester of pregnancy and that women want firsttrimester rather than later diagnosis. It is also clear that effective diagnosis of fetal abnormalities often necessitates the identification of easily recognizable markers whi...

Prenatal diagnosis of chromosomal aneuploidies is the most frequent prenatal test offered to pregnant women. In most cases, they are recommended in the following circumstances: maternal age of 35 years or above; positive firstor second-trimester screening test results, and increased risk of fetal aneuploidies due to family history. During the first trimester, screening tests include: nuchal tra...

If the protection of man against mutagenic agents in general, and against those that cause aneuploidies in particular, is to have an increasingly rational basis with the passage of time, quantitative or at least semiquantitative assessments of risks are needed. These should take into account both the likely numbers of induced cases and the likely severities of the different conditions. In the p...