Nursing: Genetic Assessment and Counselling PDF

BACHELOR OF SCIENCE IN NURSING: CARE OF MOTHER AND CHILD AT RISK OR WITH PROBLEMS (ACUTE AND CHRONIC): COURSE MODULE COURSE UNIT WEEK 1 1 1...

BACHELOR OF SCIENCE IN NURSING: CARE OF MOTHER AND CHILD AT RISK OR WITH PROBLEMS (ACUTE AND CHRONIC): COURSE MODULE COURSE UNIT WEEK 1 1 1 Genetic Assessment and Counselling Read course and unit objectives Read study guide prior to class attendance Read and understand required learning resources; refer to unit terminologies for jargons Proactively participate in online discussions Participate in weekly discussion board (Canvas) Answer and submit course unit tasks At the end of this unit, the students are expected to: Cognitive: 1. Describe the nature of inheritance, patterns of recessive and dominant mendelian inheritance, and common chromosomal aberrations that cause physical or cognitive disorders. 2. Identify National Health Goals related to genetic disorders.  3. Use critical thinking to analyze ways that can make genetic assessment or education more family centered. 4. Integrate knowledge of genetic inheritance with nursing process to achieve quality maternal and child health nursing care. Affective: Listen attentively during class discussions Demonstrate tact and respect when challenging other people’s opinions and ideas Accept comments and reactions of classmates on one’s opinions openly and graciously. Develop heightened interest in studying Maternal and Child Nursing. Psychomotor: 1. Participate actively during online class discussions and group activities 2. Express opinion and thoughts in online classes Flagg (2022). Maternal and Child Health Nursing: Care of the Childbearing and Childrearing Family. Wolters Kluwer. National Health Situation on MCN The maternal and child population is constantly changing because of changes in social structure, variations in family lifestyle, and changing patterns of illness. Client advocacy, participating in cost- containment measures, focusing on health education, and creating new nursing roles are ways in which nurses have adapted to these changes. Client advocacy is safeguarding and advancing the interests of clients and their families. The role includes knowing the health care services available in a community, establishing a relationship with families, and helping them make informed choices about what course of action or service would be best for them. National health goals are intended to help citizens more easily understand the importance of health promotion and disease prevention and to encourage wide participation in improving health in the next decade. It is important for maternal and child health nurses to be familiar with these goals because nurses play such a vital role in helping the nation achieve these objectives through both practice and research. The goals also serve as the basis for grant funding and financing of evidence-based practice. Focus on National Health Goals (Leading Health Indicators): Physical Activity Mental Health Overweight and Obesity Injury and Violence Tobacco use Environmental Quality Substance abuse Immunization Responsible sexual behavior Access to Health Care Genetic Disorders Inherited or genetic disorders are disorders that can be passed from one generation to the next. They result from some disorder in gene or chromosome structure and occur in 5% to 6% of newborns. Genetics is the study of the way such disorders occur. Cytogenetics is the study of chromosomes by light microscopy and the method by which chromosomal aberrations are identified. Genetic disorders may occur when an ovum and sperm fuse or even earlier, in the meiotic division phase of the gametes (ovum and sperm). Some genetic abnormalities are so severe that normal fetal growth cannot continue past that point. This early cell division is so precarious a process, in fact, that up to 50% of first-trimester spontaneous miscarriages may be the result of chromosomal abnormalities. Other genetic disorders do not affect life in utero, so the result of the disorder becomes apparent only at the time of fetal testing or after birth. Women having in vitro fertilization (IVF) can have both the egg and sperm examined for genetic disorders of single gene or chromosome concerns before implantation. Nature of Inheritance Genes are the basic units of heredity that determine both the physical and cognitive characteristics of people. Composed of segments of DNA (deoxyribonucleic acid), they are woven into strands in the nucleus of all body cells to form chromosomes. In humans, each cell, except for the sperm and ovum, contains 46 chromosomes (22 pair of autosomes and 1 pair of sex chromosomes). Spermatozoa and ova each carry only half of the chromosome number, or 23 chromosomes. For each chromosome in the sperm cell, there is a like chromosome of similar size and shape and function (autosome, or homologous chromosome) in the ovum. Because genes are always located at fixed positions on chromosomes, two like genes (alleles) for every trait are represented in the ovum and sperm on autosomes. The one chromosome in which this does not occur is the chromosome for determining gender. If the sex chromosomes are both type X (large symmetric) in the zygote formed from the union of a sperm and ovum, the individual is female. If one sex chromosome is an X and one a Y (a smaller type), the individual is a male. A person’s phenotype refers to his or her outward appearance or the expression of genes. A person’s genotype refers to his or her actual gene composition. It is impossible to predict a person’s genotype from the phenotype, or outward appearance. A person’s genome is the complete set of genes present (about 50,000 to 100,000). A normal genome is abbreviated as 46XX or 46XY (designation of the total number of chromosomes plus a graphic description of the sex chromosomes present). Mendelian Inheritance: Dominant and Recessive Patterns A person who has two like genes for a trait—two healthy genes, for example (one from the mother and one from the father)—on two like chromosomes is said to be homozygous for that trait. If the genes differ (a healthy gene from the mother and an unhealthy gene from the father, or vice versa), the person is said to be heterozygous for that trait. Many genes are dominant in their action over others. When paired with nondominant (recessive) genes, dominant genes. are always expressed in preference to the recessive genes. An individual with two homozygous genes for a dominant trait is said to be homozygous dominant; an individual with two genes for a recessive trait is homozygous recessive. Inheritance of Disease 1. Autosomal Dominant Disorders With an autosomal dominant condition, either a person has two unhealthy genes (is homozygous dominant) or is heterozygous, with the gene causing the disease stronger than the corresponding healthy recessive gene for the same trait. If a person who is heterozygous for an autosomal dominant trait (the usual pattern) mates with a person who is free of the trait, the chances are even (50%) that a child born to the couple would have the disorder or would be disease and carrier free (i.e., carrying no affected gene for the disorder). Two heterozygous people with a dominantly inherited disorder are unlikely to choose each other as reproductive partners. If they do, however, their chances of having children free from the disorder decline. There would be only a 25% chance of a child’s being disease and carrier free, a 50% chance that the child would have the disorder as both parents do, and a 25% chance that a child would be homozygous dominant (i.e., have two dominant disorder genes), a condition that probably would be incompatible with life. In assessing family genograms (maps of family relationships) for the incidence of inherited disorders, a few common findings are usually discovered when a dominantly inherited pattern is present in a family: One of the parents of a child with the disorder also will have the disorder (a vertical transmission picture). The sex of the affected individual is unimportant in terms of inheritance. There is usually a history of the disorder in other family members. 2. Autosomal Recessive Inheritance These inheritances tend to be biochemical or enzymatic. Such diseases do not occur unless two genes for the disease are present. Examples include cystic fibrosis, adrenogenital syndrome, albinism, Tay-Sachs disease, galactosemia, phenylketonuria, limb-girdle muscular dystrophy, and Rh factor incompatibility. When family genograms are assessed for the incidence of inherited disease, situations commonly discovered when a recessively inherited disease is present in the family include:  Both parents of a child with the disorder are clinically free of the disorder. The sex of the affected individual is unimportant in terms of inheritance. The family history for the disorder is negative—that is, no one can identify anyone else who had it (a horizontal transmission pattern). A known common ancestor between the parents sometimes exists. This explains how both male and came to possess a like gene for the disorder. 3. X-Linked Dominant Inheritance Some genes for disorders are located on, and therefore transmitted only by, the female sex chromosome (the X chromosome). If the affected gene is dominant, only one X chromosome with the trait need be present for symptoms of the disorder to be manifested. Family characteristics seen with this type of inheritance usually include: All individuals with the gene are affected (the gene is dominant). All female children of affected men are affected; all male children of affected men are unaffected. It appears in every generation. All children of homozygous affected women are affected. Fifty percent of the children of heterozygous affected women are affected. 4. X-Linked Recessive Inheritance Most X-linked inherited disorders are not dominant, but recessive. When the inheritance of a recessive gene comes from both parents (homozygous recessive) it appears to be incompatible with life. Therefore, females who inherit the affected gene will be heterozygous, and, because a normal gene is also present, the expression of the disease will be blocked. On the other hand, because males have only one X chromosome, the disease will be manifested in any male children who receive the affected gene from their mother. Hemophilia A and Christmas disease (blood- factor deficiencies), color blindness, Duchenne (pseudohypertrophic) muscular dystrophy, and fragile X syndrome (a cognitive challenge  syndrome) are examples of this type of inheritance. In this inheritance pattern, the mother has the affected gene on one of her X chromosomes and the father is disease-free. When this occurs, the chances are 50% that a male child will manifest the disease and 50% that a female child will carry the disease gene. If the father has the disease and chooses a sexual partner who is free of the disease gene, the chances are 100% that a daughter will have the sex- linked recessive gene, but there is no chance that a son will have the disease. When X-linked recessive inheritance is present in a family, a family genogram will reveal: Only males in the family will have the disorder. A history of girls dying at birth for unknown reasons often exists (females who had the affected gene on both X chromosomes). Sons of an affected man are unaffected. The parents of affected children do not have the disorder 5. Multifactorial (Polygenic) Inheritance Many childhood disorders such as heart disease, diabetes, pyloric stenosis, cleft lip and palate, neural tube disorders, hypertension, and mental illness tend to have a higher-than usual incidence in some families. They appear to occur from multiple gene combinations possibly combined with environmental factors. Diseases caused by multiple factors this way do not follow Mendelian laws because more than a single gene or HLA is involved. It may be more difficult for parents to understand why these disorders occur because their incidence is so unpredictable. A family history, for instance, may reveal no set pattern. Some of these conditions have a predisposition to occur more frequently in one sex (cleft palate occurs more often in girls than boys), but they can occur in either sex. 6. Imprinting Imprinting refers to the differential expression of genetic material and allows researchers to identify whether the chromosomal material has come from the male or female parent. Chromosomal Abnormalities (cytogenic Disorders) In some instances of genetic disease, the abnormality occurs not because of dominant or recessive gene patterns but through a fault in the number or structure of chromosomes which results in missing or distorted genes. When chromosomes are photographed and displayed, the resulting arrangement is termed a karyotype. The number of chromosomes and specific parts of chromosomes can be identified by karyotyping or by a process termed fluorescent in situ hybridization (FISH). 1. Nondisjunction Abnormalities Meiosis is the type of cell division in which the number of chromosomes in the cell is reduced to the haploid (half) number for reproduction (i.e., 23 rather than 46 chromosomes). All sperm and ova undergo a meiosis cell division early in formation. During this division, half of the chromosomes are attracted to one pole of the cell and half to the other pole. The cell then divides cleanly, with 23 chromosomes in the first new cell and 23 chromosomes in the second new cell. Chromosomal abnormalities occur if the division is uneven (nondisjunction). The result may be that one new sperm cell or ovum has 24 chromosomes and the other has only 22. If a spermatozoon or ovum with 24 or 22 chromosomes fuses with a normal spermatozoon or ovum, the zygote (sperm and ovum combined) will have either 47 or 45 chromosomes, not the normal 46. The presence of 45 chromosomes does not appear to be compatible with life, and the embryo or fetus probably will be aborted. 2. Deletion Abnormalities  Deletion abnormalities are a form of chromosome disorder in which part of a chromosome breaks during cell division, causing the affected person to have the normal number of chromosomes plus or minus an extra portion of a chromosome. 3. Translocation Abnormalities Translocation abnormalities are perplexing situations in which a child gains an additional chromosome through another route. A form of Down syndrome occurs as an example of this. In this instance, one parent of the child has the correct number of chromosomes (46), but chromosome 21 is misplaced; it is abnormally attached to another chromosome, such as chromosome 14 or 15. The parent’s appearance and functioning are normal because the total chromosome count is a normal 46. He or she is termed a balanced translocation carrier. If, during meiosis, this abnormal chromosome 14 (carrying the extra 21 chromosome) and a normal chromosome 21 from the other parent are both included in one sperm or ovum, the resulting child will have a total of 47 chromosomes because of the extra number 21. Such a child is said to have an unbalanced translocation syndrome. The phenotype (appearance) of the child will be indistinguishable from that of a child with the form of Down syndrome that occurs from simple nondisjunction. 4. Mosaicism Mosaicism is an abnormal condition that is present when the nondisjunction disorder occurs after fertilization of the ovum, as the structure begins mitotic (daughter-cell) division. If this occurs, different cells in the body will have different chromosome counts. The extent of the disorder depends on the proportion of tissue with normal chromosome structure to tissue with abnormal chromosome constitution. 5. Isochromosomes If a chromosome accidentally divides not by a vertical separation but by a horizontal one, a new chromosome with mismatched long and short arms can result. This is an isochromosome. It has much the same effect as a translocation abnormality when an entire extra chromosome exists. Genetic Counselling Any individual concerned about the possibility of transmitting a disease to his or her children should have access to genetic counseling for advice on the inheritance of disease. Such counseling can serve to: Provide concrete, accurate information about the process of inheritance and inherited disorders. Reassure people who are concerned that their child may inherit a particular disorder that the disorder will not occur. Allow people who are affected by inherited disorders to make informed choices about future reproduction. Offer support to people who are affected by genetic disorders Genetic counseling can result in making individuals feel “well” or free of guilt for the first time in their lives if they discover that the disorder, they were worried about was not an inherited one but was rather a chance occurrence. It is essential that information revealed in genetic screening be kept confidential, because such information could be used to damage a person’s reputation or harm a future career or relationship. This necessity to maintain confidentiality prevents health care providers from alerting other family members about the inherited characteristic unless the member requesting genetic assessment has given consent for the information to be revealed. In some instances, a genetic history reveals information, such as that a child has been adopted or is the result of artificial insemination, or that a current husband is not the child’s father information that a family doesn’t want revealed. The member of the family seeking counseling has the right to decide whether this information may be shared with other family members. The ideal time for counseling is before a first pregnancy. Some couples take this step even before committing themselves to marriage so they can offer not to involve their partner in a marriage if children of the marriage would be subject to a serious inherited disorder. Other couples first become aware of the need for genetic counseling after the birth of a first child with a disorder. It is best if they receive counseling before a second pregnancy. A couple may not be ready for this, however, until the initial shock of their first child’s condition and the grief reaction that may accompany it have run their course. Only then are they ready for information and decision making. Even if a couple decides not to have any more children, it is important that they know that genetic counseling is available should their decision change. Also be certain that they are aware that as their children reach reproductive age, they, too, may benefit from genetic counseling. Couples who are most apt to benefit from a referral for genetic testing or counseling include: A couple who has a child with a congenital disorder or an inborn error of metabolism. Many congenital disorders occur because of teratogenic invasion during pregnancy that has gone unrecognized. Learning that the abnormality occurred by chance rather than inheritance is important, because the couple will not have to spend the remainder of their childbearing years in fear that another child may be born with the disorder (although a chance circumstance could occur again). If a definite teratogenic agent, such as a drug a woman took during pregnancy, can be identified, the couple can be advised about preventing this occurrence in a future pregnancy. A couple whose close relatives have a child with a genetic disorder such as a translocation disorder or an inborn error of metabolism. It is difficult to predict the expected occurrence of many “familial” or multifactorial disorders. In these instances, counseling should be aimed at educating the couple about the disorder, treatment available, and the prognosis or outcome of the disorder. Based on this information, the couple can make an informed reproductive choice about children. Any individual who is a known balanced translocation carrier. Understanding of his or her own chromosome structure and the process by which future children could be affected can help such an individual make an informed choice about reproduction or can alert him or her to the importance of fetal karyotyping during any future pregnancy. Any individual who has an inborn error of metabolism or chromosomal disorder. Any person with a disease should know the inheritance pattern of the disease and, like those who are balanced translocation carriers, should be aware if prenatal diagnosis is possible for his or her disorder. A consanguineous (closely related) couple. The more closely related are two people, the more genes they have in common, so the more likely it is that a recessively inherited disease will be expressed. A brother and sister, for example, have about 50% of their genes in common; first cousins have about 12% of their genes in common. Any woman older than 35 years and any man older than 55 years. This is directly related to the association between advanced parental age and the occurrence of Down syndrome. Couples of ethnic backgrounds in which specific illnesses are known to occur. Mediterranean people, for example, have a high incidence of thalassemia, a blood disorder; those with a Chinese ancestry have a high incidence of glucose-6- phosphate dehydrogenase (G6PD) deficiency, a blood disorder where destruction of red cells can occur. Nursing Responsibilities Nurses play important roles in assessing for signs and symptoms of genetic disorders, in offering support to individuals who seek genetic counseling, and in helping with reproductive genetic testing procedures by such actions as: 1. Explaining to a couple what procedures they can expect to undergo. 2. Explaining how different genetic screening tests are done and when they are usually offered. 3. Supporting a couple during the wait for test results. 4. Assisting couples in values clarification, planning, and decision making based on test results. Genetic Disorders Assessment 1. History a. Obtain information and document diseases in family members for a minimum of three generations. Remember to include half brothers and sisters or anyone related in any way as family. b. Document the mother’s age because some disorders increase in incidence with age. c. Document also whether the parents are consanguineous or related to each other. d. Documenting the family’s ethnic background can reveal risks for certain disorders that occur more commonly in some ethnic groups than others. If the couple seeking counseling is unfamiliar with their family history, ask them to talk to senior family members about other relatives (grandparents, aunts, uncles) before they come for an interview. Have them ask specifically for instances of spontaneous miscarriage or children in the family who died at birth. e. Extensive prenatal history of any affected person should be obtained to determine whether environmental conditions could account for the condition. 2. Physical Assessment a. A careful physical assessment of any family member with a disorder, child’s siblings, and the couple seeking counseling is needed. It is possible for an individual to have a minimal expression of a disorder that has gone previously undiagnosed. b. During inspection, pay particular attention to certain body areas, such as the space between the eyes; the height, contour, and shape of ears; the number of fingers and toes, and the presence of webbing. Dermatoglyphics (the study of surface markings of the skin) can also be helpful. Note any abnormal fingerprints or palmar creases as these are present with some disorders. Abnormal hair whorls or coloring of hair can also be present. c. Careful inspection of newborns is often sufficient to identify a child with a potential chromosomal disorder. Infants with multiple congenital anomalies, those born at less than 35 weeks’ gestation, and those whose parents have had other children with chromosomal disorders need extremely close assessment. 3. Diagnostic Testing a. Karyotyping A sample of peripheral venous blood or a scraping of cells from the buccal membrane is taken. Cells are allowed to grow until they reach metaphase, the most easily observed phase. Cells are then stained, placed under a microscope, and photographed. Chromosomes are identified according to size, shape, and stain; cut from the  photograph, and arranged. Any additional, lacking, or abnormal chromosomes can be visualized by this method. A newer method of staining, FISH, allows karyotyping to be done immediately, rather than waiting for the cells to reach metaphase. This makes it possible for a report to be obtained in only 1 day. Fetal skin cells can be obtained by amniocentesis or CVS. A few fetal cells circulate in the maternal bloodstream, most noticeably trophoblasts, lymphocytes, and granulocytes. They are present but few during the first and second trimesters but plentiful during the third trimester. Such cells can be cultured and used for genetic testing for such disorders as the trisomy. b. Maternal Serum Screening Alpha-fetoprotein (AFP) is a glycoprotein produced by the fetal liver that reaches a peak in maternal serum between the 13th and 32nd week of pregnancy. Most pregnant women have an MSAFP test done routinely at the 15th week of pregnancy. If the result is abnormal, amniotic fluid is then assessed. Unfortunately, the MSAFP test has a false-positive rate of about 30% if the date of conception is not well documented. Use of a “triple study” (AFP, estriol, and hCG) reduces this false-positive rate, although false-positive reports still occur. c. Chorionic Villi Sampling CVS is a diagnostic technique that involves the retrieval and analysis of chorionic villi from the growing placenta for chromosome or DNA analysis. The test is highly accurate and yields no more false-positive results than does amniocentesis. Although this procedure may be done as early as week 5 of pregnancy, it is more commonly done at 8 to 10 weeks. With this technique, the chorion cells are located by ultrasound. A thin catheter is then inserted vaginally, or a biopsy needle is inserted abdominally or intravaginally, and several chorionic cells are removed for analysis. CVS carries a small risk (less than 1%) of causing excessive bleeding, leading to pregnancy loss. After CVS, instruct a woman to report chills or fever suggestive of infection or symptoms of threatened miscarriage (uterine contractions or vaginal bleeding). Women with an Rh-negative blood type need Rh immune globulin administration after the procedure to guard against isoimmunization in the fetus. The cells removed in CVS are karyotyped or submitted for DNA analysis to reveal whether the fetus has a genetic disorder. Because chorionic villi cells are rapidly  dividing, results are available quickly, perhaps as soon as the next day. If a twin or multiple pregnancy is present, with two or more separate placentas, cells should be removed separately from each placenta. Because fraternal twins are derived from separate ova, one twin could have a chromosomal abnormality while the other does not. d. Amniocentesis Amniocentesis is the withdrawal of amniotic fluid through the abdominal wall for analysis at the 14th to 16th week of pregnancy. Because amniotic fluid has reached about 200 mL at this point, enough fluid can be withdrawn for karyotyping of skin cells found in the fluid as well as an analysis of AFP or acetylcholinesterase. For the procedure, a pocket of amniotic fluid is located by ultrasound. Then a needle is inserted transabdominally, and about 20 mL of fluid is aspirated. e. Percutaneous Umbilical Blood Sampling PUBS, or cordocentesis, is the removal of blood from the fetal umbilical cord at about 17 weeks using an amniocentesis technique. This allows analysis of blood components as well as more rapid karyotyping than is possible when only skin cells are removed. f. Fetal imaging Magnetic resonance imaging (MRI) and ultrasound are diagnostic tools used to assess a fetus for general size and structural disorders of the internal organs, spine, and limbs. Because some genetic disorders are associated with physical appearance, both methods may be helpful. Ultrasound is used concurrently with amniocentesis. g. Fetoscopy Fetoscopy is the insertion of a fiberoptic fetoscope through a small incision in the mother’s abdomen into the uterus and membranes to visually inspect the fetus for gross abnormalities. It can be used to confirm an ultrasound finding, to remove skin cells for DNA analysis, or to perform surgery for a congenital disorder such as a stenosed urethra.  h. Preimplantation Diagnosis Preimplantation diagnosis is possible for in vitro fertilization procedures. It may be possible in the future for a naturally fertilized ovum to be removed from the uterus by lavage before implantation and studied for DNA analysis this same way. The ovum would then be reinserted or not, depending on the findings and the parents’ wishes. This would provide genetic information extremely early in a pregnancy. Chromosome – the structure that weaves genes into strands in the nucleus of all body cells. Genes – basic units of heredity that determine both the physical and mental characteristics of people. Genetics – study of how and why chromosomal disorders occur; the science of heredity. Genome – complete set of genes present Genotype – actual gene composition Website: fact-sheet-9-x-linked-recessive-inheritance (genetics.edu.au) Study Questions Download a research article on the topic ‘Genetic Assessment and Counselling’ from ScienceDirect. Submit a 300-word essay reflection. Flagg (2022). Maternal and Child Health Nursing: Care of the Childbearing and Childrearing Family. Wolters Kluwer.