Over the last few decades, prenatal diagnosis has become more and more extensive and important. This trend dates back to the discovery of the human karyotype by Tjio and Levan in 1956. In the years following this discovery, numerous congenital anomalies resulting from chromosome aberrations were detected. Today, mainly as the result of advances in and continuous enhancement of tissue-sampling and cellcultivation techniques, certain foetal diseases can be investigated and diagnosed even during pregnancy. Amniocentesis, which made sex determination from amniocytes possible for the first time as early as in 1956 and thus confirmed the high predictive value of this method. Foetal cells obtained from amniotic fluid were cultivated successfully for the first time in 1966. The introduction of banding techniques opened up even further diagnostic avenues between 1968 and, as did above ail, the development of ultrasonic procedures in the second half of the 1970s. In addition to chromosome analysis at various stages of gestation, methods for detecting monogenic mutations also have been developed. Such mutations can be identified with the help of gene product analyses and, in cases involving a known genetic defect, directly by DNA analyses.
Ultrasonography for the prenatal diagnosis of congenital abnormalities has evolved over the last decades. The aim of this method is to reliably diagnose or, in the vast majority of cases, to exclude the presence of anomalies. 98% of routine ultrasound scans serve to reassure parents and therefore reduce much anxiety. Ultrasound is used commonly to date the gestational age accurately, to monitor foetal growth, to localize the placenta, to monitor the amount of amniotic fluid and to detect multiple pregnancies. However, opinions regarding the place and advantages of routine foetal anomaly screening differ widely in the United States and many European countries.
A common misconception present among the lay population and professionals is that prenatal diagnosis is concerned chiefly with the detection of foetal chromosomal aberrations, most specifically trisomy 21. Because no therapy for such chromosomal abnormalities exists, prenatal diagnosis often is characterized (to use William Liley's words) as a "search and destroy mission". In reality, prenatal medicine, as we prefer to call it, represents one of the most inter-active multidisciplinary, technology-driven medical sciences, involving obstetricians, genetic counsellors, cytogeneticists, biochemists and molecular biologists. The incorporation and adaptation of new technologies is so intense in prenatal diagnosis and, more recently, in related therapies, that several facets of this area, such as the examination of preimplantation embryos and non-invasive prenatal investigations performed on maternal blood, can be regarded safely as being «cutting edge» in character.
Prenatal diagnosis has been a medical concern for over a hundred years. However, it entered medical practice only in the fifties with the prenatal diagnosis of a foetus' gender, using amniotic fluid cells . When Fuchs et al. reported in 1956 the practicality of chromatin determination in cells from human amniotic fluid obtained by amniocentesis, the in utero cytogenetic study of the human foetus became theoretically possible by culturing those cells . It is worth noting that true number of chromosomes in the human species, i.e. 46, was ascertained in 1956 by Tjio and Levan . The practicality of the method was shown by 1962 and in 1966 Steele and Breg published "the first analysis of human amnioticfluid cells" .
In most countries, pregnant women undergo sonography two or three times during pregnancy. Cost benefit and effectiveness analyses are discussed in detail by the authors to reinforce the importance of the quality of the investigation.
The more sophisticated prenatal diagnosis has become over the last decades, the more difficult is the ethical question. Jean Frézal and Marie-Louise Briard, Paris V University, France, provide an insightful review of the ethical implications of prenatal diagnoses. The potential stigmatization of the unborn, the question of elective abortions and the appropriate role of parental genetic counseling are among the issues discussed in their article. Should a list of diseases for prenatal diagnosis be developed? Who should decide what to do when a severe condition is diagnosed? Is confidentiality always assured? Such questions are raised by the authors and appropriate approaches for developing answers, matters of ongoing debate, are reviewed.