Genetic Testing During and Before Pregnancy

Genetic testing is performed through the analysis of small blood or body tissue samples. They determine whether you, your partner or your baby carry genes for certain inherited disorders. Genetic testing has developed enough so that doctors can often identify missing or defective genes. The type of genetic test needed to make a specific diagnosis depends on the particular disease a doctor suspects. Many different types of body fluids and tissues may be used in genetic testing. Only a very small bit of blood, skin, bone, or other tissue is needed for deoxyribonucleic acid (DNA) screening.

Genetic Testing During Pregnancy

Pregnant women may choose to undergo amniocentesis or chorionic villus sampling for genetic testing before birth. Women also have a blood test available to screen for certain disorders. If this screening test has a potential problem, it may be recommended to sample amniocentesis or chorionic villus.

Amniocentesis is a test of a woman's pregnancy usually carried out between weeks 15 and 20. The doctor inserts a hollow needle into the abdomen of the woman to remove from the developing fetus a small amount of amniotic fluid. This fluid can be tested to determine the child's sex and genetic problems. When the risk of premature birth occurs, amniocentesis can be done to see how far the lungs of the baby have matured. Amniocentesis is associated with a slight risk of miscarriage.

A sampling of chorionic villus (CVS) usually takes place between the 10th and 12th weeks of pregnancy. To check for genetic problems in the fetus, the doctor removes a small piece of the placenta. Since chorionic villus sampling is an invasive test, there is a small risk that a miscarriage may occur.