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Genetic counseling aims to facilitate the exchange of information regarding a person's genetic legacy. It attempts to:
- accurately diagnose a disorder
- assess the risk of recurrence in the concerned family members and their relatives
- provide alternatives for decision-making
- provide support groups that will help family members cope with the recurrence of a disorder.
Genetic counselors work with people concerned about the risk of an inherited disease. The counselor does not prevent the incidence of a disease in a family, but can help family members assess the risk for certain hereditary diseases and offer guidance. Many couples seek genetic counseling because there is a family history of known genetic disorders, infertility, miscarriage, still births, or early infant mortality. Other reasons for participating in genetic counseling may be the influences of a job or lifestyle that exposes a potential parent to health risks such as radiation, chemicals, or drugs. Any family history of mental retardation can be of concern as is a strong family history of heart disease at an early age. Recent statistics show a 3% chance of delivering a baby with birth defects. An additional 2% chance of having a baby with Down syndrome is present for women in their late thirties and older.
Genetic counseling may take on new emphasis in the near future as genetic research continues to advance. In April 2003, the Human Genome Project announced completion of mapping the entire human genetic makeup. The project identified more than 1,400 disease genes and completed study of the ethical, legal, and social issues raised by this expanded knowledge of human genetics. As knowledge expands and scientists discover more methods to identify and treat various diseases, people will face more difficult decisions about their own genetic information.
Amniocentesis, one of the specific tests used to gather information for genetic counseling, is best performed between weeks 15 and 17 of a pregnancy and an additional one to four weeks may be required to culture skin cells and analyze them. Thus, these test data are not available to assist prospective parents in decision-making until the second trimester of the pregnancy. Individuals who participate in genetic counseling and associated testing also must be aware that there are no cures or treatments for some of the disorders that may be identified.
With approximately 2,000 genes identified and approximately 5,000 disorders caused by genetic defects, genetic counseling is important in the medical discipline of obstetrics. Genetic counselors, educated in the medical and the psychosocial aspects of genetic diseases, convey complex information to help people make life decisions. There are limitations to the power of genetic counseling, though, since many of the diseases that have been shown to have a genetic basis currently offer no cure (for example, Down syndrome or Huntington's disease). Although a genetic counselor cannot predict the future unequivocally, he or she can discuss the occurrence of a disease in terms of probability.
Genetic counseling also can help people with diseases they may face in their own lifetimes. A 2003 study in Great Britain found that women with a family history of breast cancer were less worried about getting the disease if they had genetic counseling.
A genetic counselor, with the aid of the patient or family, creates a detailed family pedigree that includes the incidence of disease in first-degree (parents, siblings, and children) and second-degree (aunts, uncles, and grandparents) relatives. Before or after this pedigree is completed, certain genetic tests are performed using DNA analysis, x ray, ultrasound, urine analysis, skin biopsy, and physical evaluation. For a pregnant woman, prenatal diagnosis can be made using amniocentesis or chorionic villus sampling.
An important aspect of the genetic counseling session is the compilation of a family pedigree or medical history. To accurately assess the risk of inherited diseases, information on three generations, including health status and/or cause of death, usually is needed. If the family history is complicated, information from more distant relatives may be helpful, and medical records may be requested for any family members who have had a genetic disorder. Through an examination of the family history a counselor may be able to discuss the probability of future occurrence of genetic disorders. In all cases, the counselor provides information in a non-directive way that leaves the decision-making up to the client.
Family history questionnaire
As more detailed genetic information becomes available, physicians and genetic counselors may feel the need to dig more deeply than a family pedigree allows. In 2004, physicians attending an American College of Medical Genetics meeting announced use of a structured questionnaire with 50 items to consistent, thorough gather family history data. Although the questionnaire's format and terminology were confusing to some patients, once a formula was applied to the answers, it still helped reviewers agree on a counseling plan 79% of the time.
Screening blood tests help identify individuals who carry genes for recessive genetic disorders. Screening tests usually are only done if:
- The disease is lethal or causes severe handicaps or disabilities.
- The person is likely to be a carrier due to family pedigree or membership in an at-risk ethnic, geographic or racial group.
- The disorder can be treated or reproductive options exist.
- A reliable test is available.
Genetic disorders such as Tay-Sachs disease, sickle-cell anemia, and thalassemia meet these criteria, and screening tests are commonly done to identify carriers of these diseases. In addition, screening tests may be done for individuals with family histories of Huntington's disease (a degenerative neurological disease) or hemophilia (a bleeding disorder). Such screening tests can eliminate the need for more invasive tests during a pregnancy.
Another screening test commonly used in the United States in the alpha-fetoprotein (AFP) test. This test is done on a sample of maternal blood around week 16 of a pregnancy. An elevation in the serum AFP level indicates that the fetus may have certain birth defects such as neural tube defects (including spina bifida and anencephaly). If the test yields an elevated result, it may be run again after seven days. If the level still is elevated after repeat testing, additional diagnostic tests (e.g. ultrasound and/or amniocentesis) are done in an attempt to identify the specific birth defect present.
Ultrasound is a noninvasive procedure that uses sound waves to produce a reflected image of the fetus upon a screen. It is used to determine the age and position of the fetus, and the location of the placenta. Ultrasound also is useful in detecting visible birth defects such as spina bifida (a defect in the development of the vertebrae of the spinal column and/or the spinal cord). It also is useful for detecting heart defects, and malformations of the head, face, body, and limbs. This procedure, however, cannot detect biochemical or chromosomal alterations in the fetus.
Amniocentesis is useful in determining genetic and developmental disorders not detectable by ultrasound. This procedure involves the insertion of a needle through the abdomen and into the uterus of a pregnant woman. A sample of amniotic fluid is withdrawn containing skin cells that have been shed by the fetus. The sample is sent to a laboratory where fetal cells contained in the fluid are isolated and grown in order to provide enough genetic material for testing. This takes about seven to 14 days. The material then is extracted and treated so that visual examination for defects can be made. For some disorders, like Tay-Sachs disease, the simple presence of a telltale chemical compound in the amniotic fluid is enough to confirm a diagnosis.
While it has been routine in recent years to suggest amniocentesis to every pregnant woman age 35 and older to screen for Down syndrome, evidence in 2003 began suggesting that it made more sense and was safer to offer blood test screening. The "triple screen" blood test can identify about three-fourths of Down syndrome cases by measuring certain chemicals in the mother's blood.
Chorionic villus sampling
Chorionic villus sampling involves the removal of a small amount of tissue directly from the chorionic villi (minute vascular projections of the fetal chorion that combine with maternal uterine tissue to form the placenta). In the laboratory, the chromosomes of the fetal cells are analyzed for number and type. Extra chromosomes, such as are present in Down syndrome, can be identified. Additional laboratory tests can be performed to look for specific disorders and the results usually are available within a week after the sample is taken. The primary benefit of this procedure is that it is usually performed between weeks 10 and 12 of a pregnancy, allowing earlier detection of fetal disorders. A 2003 study reported that this test resulted in fewer cases of pregnancy loss, amniotic fluid leakage, or birth defects than early amniocentesis.
Genetic diagnosis requires that a couple share information about inherited disorders in their background with the genetic counselor, including details of any genetic diseases in either family. A couple undergoing genetic counseling also reports any past miscarriages and discusses the possibility of exposure to chemicals, radiation (including x rays), or other occupational environmental hazards. The couple also needs to disclose information about personal habits before or during pregnancy such as drug or alcohol abuse and the use of prescription or over-the-counter drugs taken by the mother since the beginning of pregnancy. The genetic counselor explains the procedures used in testing that will be done and describes what each test can and cannot reveal.
Genetic counseling provides couples with information that can help them make decisions about future pregnancies. It also gives couples additional time to emotionally prepare if a disorder is detected in the fetus. The counselor discusses the results of testing and informs the couple if a problem is apparent. The doctor or genetic counselor also discusses the treatment options available. Genetic counseling is done in a non-directive way, so that any treatment selected remains the personal choice of the individuals involved. Genetic counseling can provide information essential for family planning and pregnancy management, thus maximizing the chances of a positive outcome.
Because prenatal testing, such as amniocentesis and chorionic villus sampling, is invasive and carries a 1% risk of miscarriage it should never be considered routine.
Screening tests and/or prenatal tests reveal no birth defects or genetic abnormalities.
A birth defect or genetic disorder is detected. The early diagnosis of birth defects and genetic disorders allows a greater number of treatment options. Some disorders can be treated in utero (before birth while the fetus is still in the uterus), while others may require early delivery, immediate surgery, or cesarean section to minimize fetal trauma. Prior warning of fetal difficulties allows parents time to prepare emotionally for the birth of the child. In some instances, termination of the pregnancy may be chosen. Whatever the test results, this information is essential for family planning and pregnancy management.
"Best Early Test." Fit Pregnancy (October-November, 2003): 37.
"Blood Test Screening Reduces Need for Amniocentesis." Womenós Health Weekly (December 4, 2003): 51.
Bodenhorn, Nancy, and Gerald Lawson. "Genetic Counseling: Implications for Community Counselors." Journal of Counseling and Development (Fall 2003): 497-495.
"Genetic Counseling Questionnaire Helps Assess FamilyÆs Genetic History." Internal Medicine News (April 15, 2004): 45.
"Genetic Counseling Reduces WomenÆs Fears." Womenós Health Weekly (September 11, 2003): 23.
Wechsler, Jill. "From Genome Exploration to Drug Development." Pharmaceutical Technology Europe (June 2003): 18-23.
American Medical Association. 515 N. State St., Chicago, IL 60612. (312) 464-5000. http://www.amaassn.org.
American Society of Human Genetics. 9650 Rockville Pike, Bethesda, MD 20814-3998. (301) 571-1825. http://www.faseb.org/genetics/ashg/ashgmenu.htm.
March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (914) 428-7100. email@example.com. http://www.modimes.org.
Sickle-cell anemia — A chronic, inherited blood disorder characterized by crescent-shaped red blood cells. It occurs primarily in people of African descent, and produces symptoms including episodic pain in the joints, fever, leg ulcers, and jaundice.
Tay-Sachs disease — A hereditary disease affecting young children of eastern European Jewish descent. This disease is caused by an enzyme deficiency leading to the accumulation of gangliosides (galactose-containing cerebrosides) found in the surface membranes of nerve cells in the brain and nerve tissue. This deficiency results in mental retardation, convulsions, blindness, and, finally, death.
Thalassemia — An inherited group of anemias occurring primarily among people of Mediterranean descent. It is caused by defective formation of part of the hemoglobin molecule.
in the nursing interventions classification, a nursing intervention defined as use of an interactive helping process focusing on the needs, problems, or feelings of the patient and significant others to enhance or support coping, problem solving, and interpersonal relationships.
genetic counseling in the nursing interventions classification, a nursing intervention defined as use of an interactive helping process focusing on assisting an individual, family, or group, manifesting or at risk for developing or transmitting a birth defect or genetic condition, to cope.
lactation counseling in the nursing interventions classification, a nursing intervention defined as the use of an interactive helping process to assist in maintenance of successful breastfeeding.
nutritional counseling in the nursing interventions classification, a nursing intervention defined as the use of an interactive helping process focusing on the need for diet modification.
preconception counseling in the nursing interventions classification, a nursing intervention defined as providing information and support to individuals of childbearing age before pregnancy to promote health and reduce risk.
sexual counseling in the nursing interventions classification, a nursing intervention defined as the use of an interactive helping process focusing on the need to make adjustments in sexual practice or to enhance coping with a sexual event or disorder.
the process whereby an expert in genetic disorders provides information about risk and clinical burden of a disorder or disorders to patients or relatives in families with genetic disorders as an aid to making informed and responsible decisions about marriage, children, early diagnosis, and prognosis.
The counseling of individuals, and of prospective parents regarding their offspring, on the probability of inheriting genetic diseases and on their associated diagnosis and treatment.
genetic counselingClinical genetics The education of an individual, couple, or family known or suspected of being at risk for a genetic disease. See Genetic counselor.
ge·net·ic coun·sel·ing(jĕ-net'ik kown'sĕl-ing)
The process whereby an expert in genetic disorders provides information about risk and clinical burden of a disorder or disorders to patients or relatives in families with genetic disorders as an aid to making informed and responsible decisions about marriage, children, early diagnosis, and prognosis.
ge·net·ic coun·sel·ing(jĕ-net'ik kown'sĕl-ing)
The process whereby an expert in genetic disorders provides information about risk and clinical burden of a disorder or disorders to patients or relatives in families with genetic disorders.