Genetic Counseling:   

Genetic counseling is the process of:

• evaluating family history and medical records

• ordering genetic tests

• evaluating the results of this investigation

• helping parents understand and reach decisions about what to do next

Genetics is the study of how traits such as blood type, are passed from parent to child through genes and chromosomes. Each cell in your body has pairs of genes and chromosomes. They control your physical makeup. Genes are made up of DNA molecules, which are the simplest building blocks of heredity. They're grouped together in specific patterns within a person's chromosomes, forming the unique "blueprint" for every physical and biological characteristic of that person. Humans have 46 chromosomes, arranged in pairs in every living cell of our bodies. When the egg and sperm join at conception, half of each chromosomal pair is inherited from each parent. This newly formed combination of chromosomes then copies itself again and again during fetal growth and development, passing identical genetic information to each new cell in the growing fetus. An error in just one gene can sometimes be the cause for a serious medical condition. Each chromosome carries many genes. Genes also come in pairs. Half of a fetus's genes come from the mother. The other half come from the father. Some traits, such as blood type, are determined by a single gene pair. Other traits, including skin color, hair color, and height, are the result of many pairs of genes working together.

Who Should Receive Genetic Counseling?

Most couples planning a pregnancy or who are expecting don't need genetic counseling. Only a small percentage of babies are born with birth defects each year.  However, the best time to seek genetic counseling is before becoming pregnant, when the physician  can help assess your risk factors. But even after you become pregnant, meeting with a physician trained in genetic counseling can still be helpful.

You should consider genetic counseling if any of the following risk factors apply to you:

• if a standard prenatal screening test (such as the alpha fetoprotein test) yields an abnormal result

• if an amniocentesis yields an unexpected result (such as a chromosomal defect in the unborn baby)

• if either parent or a close relative has an inherited disease or birth defect

• if either parent already has children with birth defects or genetic disorders

• if the mother-to-be has had two or more miscarriages or babies that died in infancy

• if the mother-to-be will be 35 or older when the baby is born (

• if parents are concerned about genetic defects that occur frequently in their ethnic or racial group (For example, couples of African descent are most at risk for having a child with sickle cell anemia; couples of central or eastern European Jewish (Ashekenazi), Cajun, or Irish descent may be carriers of Tay-Sachs disease; and couples of Italian, Greek, or Middle Eastern descent may carry the gene for thalassemia, a red blood cell disorder.)

Screening Tests

Screening tests are available to detect some birth defects during pregnancy. However, a screening test only shows if there is an increased risk that a defect will occur. The following screening tests may be offered:

• Maternal serum screening. This test is used to find out if a woman is at increased risk for having a baby with a neural tube defect, abdominal wall defect, Down syndrome, or trisomy 18. These tests usually are done between 15 and 20 weeks of pregnancy.

• First trimester screening. This screening test combines the results of a special ultrasound test called nuchal translucency screening and blood (serum) tests (PAPP-A and hCG). It is done between 10 and 14 weeks of pregnancy. This test can be done to look for signs of Down syndrome, trisomy 18, and heart defects.

If the results of a screening test show an increased risk, further tests may be done to diagnose the problem.

Diagnostic Tests

If a screening test or other factors raise concerns, diagnostic tests often can show whether certain birth defects are present. The following diagnostic tests may be offered:

• Detailed ultrasound exam. A type of ultrasound exam that can help explain abnormal screening test results and provide more detailed information. A detailed exam is best performed after 18 weeks of pregnancy.

• Amniocentesis. A procedure in which a needle is used to withdraw a small amount of amniotic fluid and cells from the sac surrounding the fetus. The amniotic fluid and cells can be tested to detect certain chromosomal problems in the fetus. Amniocentesis usually is done at 15–20 weeks of pregnancy.

• Chorionic villus sampling (CVS). A procedure in which a small sample of cells is taken from the placenta and tested. CVS detects some of the same chromosomal problems as amniocentesis does. This test can be performed earlier than amniocentesis—often at 10–12 weeks of pregnancy.

• Fetal blood sampling. Also known as cordocentesis, this procedure tests for chromosomal defects and other problems. For this test, blood is taken from a vein in the umbilical cord. Fetal blood sampling usually is used when the results of amniocentesis, chorionic villus sampling, or ultrasound are unclear.