Prenatal detection of genetic defects.

The intrauterine detection of genetic disorders represents one of the exciting advances 
in medicine. The major emphasis in this chapter will be a 
detailed review of the newer approaches toward antenatal detection of congenital 
malformations and hemoglobinopathies as well as an overview of the experience 
and problems of antenatal detection for chromosomal aberrations and inborn errors 
of metabolism. Approaches to prenatal diagnosis of genetic disorders include amniocentesis, 
visualization of the fetus, and fetal blood sampling. Prenatal detection of 
genetic disorders has become a reality. The area is evolving so 
rapidly that the major indications for intrauterine diagnosis have substantially changed 
within the past year. Prior to this time, maternal age, previous 
Down's syndrome, inborn errors of metabolism and X-linked recessive disorders were 
the primary criteria, with approximately 85% of the cases being used 
for cytogenetic analysis. Within the past year, in a number of 
laboratories, about half of the referrals for amniocentesis have been for 
central nervous system defects. Certainly with the development of technics for 
fetal blood sampling, this distribution of the frequencies of indication may, 
once again, change substantially. Most probably for the next few years 
cytogenetic abnormalities and neural tube defects will be the most common 
indications for amniocentesis. Amniocentesis will continue to be offered to many 
patients with inborn errors of metabolism and probably will be available 
for monitoring of hemoglobinopathies and other disorders of fetal blood as 
well as for accurate knowledge of the health of the fetus. 
