HIGH-RISK PREGNANCY :: Prenatal Counseling
Types of Genetic Diseases
There are several types of genetic disorders. The way in which the disorder is inherited can help determine the risks it will have on a pregnancy and the risk it will recur in future children. Risks for having a baby with a birth defect from a genetic abnormality may be increased when:
What are the types of genetic disease?
The following are the different types of genetic diseases:
What are chromosomal abnormalities?
Chromosomal abnormalities in the baby may be inherited from the parent or may occur with no family history. The following chromosomal problems are the most common:
What are single gene disorders?
These are also known as Mendelian inheritance disorders, from the first genetic work of Gregor Mendel. In these disorders, a single gene is responsible for a defect or abnormality. Single gene disorders usually have greater risks of inheritance. Single gene disorders can be:
What are multifactorial problems?
Some birth defects do not follow a single gene or chromosomal abnormality pattern. They may be due to several problems, or a combined effect of genes and the environment. It is difficult to predict inheritance of abnormalities caused by multiple factors. Examples include heart defects, cleft lip or cleft palate, and neural tube defects (defects in the spine or brain).
What are teratogenic problems?
Certain substances are known to cause abnormalities in babies. Many birth defects occur when the fetus is exposed to teratogens (substances that cause abnormalities) during the first trimester of pregnancy when organs are forming. Some known teratogens include the following:
How are genetic problems diagnosed?
Families at risk for genetic diseases may want to consult a specialized genetics counselor. A careful family pedigree (chart of members of the family) and history may help determine risks for certain problems. Counseling also helps parents understand the effects of a disorder and ways it may be prevented or treated.
It may be necessary to check each parent's DNA to learn about some genetic inheritance patterns. Prenatal testing is also available to check the fetus for problems. Testing may include ultrasound (using sound waves to look at internal structures), chorionic villus sampling (testing the tissues around the fetus), or amniocentesis (withdrawing a sample of the amniotic fluid).
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