Prenatal diagnosis

Alternative names
Genetic counseling and prenatal diagnosis


For over 4000 years, people have noticed that certain diseases run in families, but the “why” was unknown until modern science showed how genetic information is transmitted.

Present-day medicine recognizes that genetic diseases are inherited based on the nature of DNA, genes, and chromosomes. Now that the human genome has been completely sequenced, scientists are better able to study how changes in DNA cause human disease. This will ultimately help in diagnosing and treating genetic disorders.

However, until science has the knowledge to treat some of the more serious, sometimes fatal genetic disorders, the best option is prevention. Prevention of genetically transmitted diseases can consist of major choices: abstinence from pregnancy, egg or sperm donation, preimplantation or prenatal diagnosis and termination, or early treatment of affected pregnancies.

Prenatal diagnosis involves testing fetal cells, amniotic fluid, or amniotic membranes to detect fetal abnormalities. Preimplantation diagnosis is a new technique only available in specialized centers. It involves in vitro fertilization and genetic testing of the resulting embryos prior to implanting only those embryos found not to have the abnormal gene.

Genetic counseling and prenatal diagnosis provides parents with the knowledge to make intelligent, informed decisions regarding possible pregnancy and its outcome. Based on genetic counseling, some parents (in the face of possibly lethal genetic disease) have forgone pregnancy and adopted children while others have opted for egg or sperm donation from an anonymous donor who is not likely to be a carrier of the specific disease.

Many diseases transmitted as a single gene defect can now be diagnosed very early in pregnancy. Because of this some parents choose to become pregnant and have the disease status of the fetus determined early in the pregnancy. The pregnancy is continued if the fetus is disease-free. Parents who decide to continue the pregnancy with a defective fetus may be able to better prepare to care for the infant by being informed about the disease in advance. For example, genetic diseases that have a diet intolerance component may be treated with specialized diets for the mother and newborn baby.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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