Primary Prevention of Genetic Disorders and Place of Preimplantation Genetic Diagnosis

Despite recent progress in gene therapy it is still not a realistic option for genetic disorders, prevention remaining the main approach. Preventive measures may be applied at the community level by avoiding new mutations, protecting from all possible environmental hazards, predictive testing for genetic and complex disorders, and prospective screening for common genetic disorders specific for each ethnic group. The optimal time for offering these preventive measures is preconception or preimplantation stage, as any detection afterwards will involve the decision either to keep the pregnancy with the long-term social, familial, and financial consequences of a seriously affected child, or to terminate the planned and wanted pregnancy.

So the strategies for prevention range from preventing environmental hazards and providing vitamin supplementation programs to the prepreg-nancy or prenatal diagnosis. One example of the highly effective population-based preventive measures realized at the preconception stage has been prevention of neural tube defects and some other congenital abnormalities by folic acid or folic acid-containing multivitamins. On the other hand, preconception and preimplantation genetic diagnosis (PGD) has been established as a realistic option for primary prevention of genetic disorders, which is described in the detail in this book.

The list of most relevant approaches for prevention of congenital disorders presently includes (1) the avoidance of new mutations through environmental programs, (2) discouragement of pregnancy at advanced ages through community education and family planning, (3) periconcep-tion folic acid supplementation or multivitamin fortification of basic foodstuffs, (4) rubella vaccination, (5) avoidance of alcohol consumption and smoking during pregnancy, and (6) prenatal and (7) prepregnancy (preimplantation) diagnosis. The decision to adopt any of the available preventive programmes depends on the differences in health services development, ethnic distribution of congenital disease, and the local attitudes to genetic screening and termination of pregnancy. For example, induced abortions are still not permissible in many countries on eugenic grounds. On the other hand, an increasing number of countries are gradually permitting prenatal diagnosis and termination of pregnancies for medical indications even in some strict religious settings.

The impact of the community-based preventive approaches is obvious from the Down syndrome prevention program in the majority of industrialised countries of Europe and the United States. The programs are based on the introduction of prenatal maternal serum screening for all pregnant women to detect pregnancies at increased risk, followed by prenatal diagnosis and selective pregnancy termination, combined with prenatal diagnosis offered to all women of advanced maternal age, which have resulted in the reduction of the birth prevalence of Down syndrome at least by half. However, this led to an increasing number

Was this article helpful?

0 0

Post a comment