Genetic Assessment and Counselling in Maternal and Child Nursing

Genetic Assessment and Counselling: Course Objectives and Instructional Guidance

The course unit on Genetic Assessment and Counselling for the Bachelor of Science in Nursing focuses on the care of mother and child at risk or with acute and chronic problems. Students should read the course and unit objectives and study guides prior to attending class. Learning involves understanding required resources and unit terminologies for technical jargons. Students are expected to proactively participate in online discussions, engage with the weekly discussion board on Canvas, and submit unit tasks.

Upon completion of this unit, students are expected to achieve specific cognitive, affective, and psychomotor goals. Cognitively, students must describe the nature of inheritance, patterns of recessive and dominant Mendelian inheritance, and common chromosomal aberrations causing physical or cognitive disorders. They must also identify National Health Goals related to genetic disorders, use critical thinking to analyze family-centered genetic education, and integrate genetic inheritance knowledge with the nursing process to achieve quality maternal and child health nursing care.

Affectively, students are expected to listen attentively, demonstrate tact and respect when challenging opinions, and accept classmate reactions graciously while developing an interest in Maternal and Child Nursing. From a psychomotor perspective, students must participate actively in online class discussions and group activities, expressing their opinions and thoughts effectively.

National Health Situation in Maternal and Child Nursing

The maternal and child population is in a state of constant change due to shifts in social structure, variations in family lifestyles, and changing patterns of illness. Nurses adapt to these changes through several avenues, including client advocacy, participation in cost-containment measures, focusing on health education, and the creation of new nursing roles. Client advocacy is defined as the safeguarding and advancing of the interests of clients and their families. This role involves maintaining knowledge of community health services, establishing relationships with families, and assisting them in making informed choices regarding the best course of action or service for their specific needs.

National health goals are designed to help citizens understand the importance of health promotion and disease prevention while encouraging wide participation in health improvement over the next decade. It is vital for maternal and child health nurses to be familiar with these goals, as they play a critical role in achieving these objectives through practice and research. These goals also serve as a foundational basis for grant funding and the financing of evidence-based practice.

The leading health indicators associated with these National Health Goals include: physical activity, mental health, overweight and obesity, injury and violence, tobacco use, environmental quality, substance abuse, immunization, responsible sexual behavior, and access to health care.

Fundamental Principles of Genetic Inheritance and Biological Units

Inherited or genetic disorders are conditions passed from one generation to the next, resulting from disorders in gene or chromosome structure. These occur in approximately $5\%$ to $6\%$ of newborns. Genetics is defined as the study of the way such disorders occur. Cytogenetics is the study of chromosomes via light microscopy and serves as the method for identifying chromosomal aberrations.

Genetic disorders can occur when an ovum and sperm fuse or during the meiotic division phase of gametes. Some abnormalities are so severe that fetal growth cannot continue; indeed, up to $50\%$ of first-trimester spontaneous miscarriages may result from chromosomal abnormalities. Other disorders do not affect life in utero and only become apparent during fetal testing or after birth. Women undergoing in vitro fertilization ($IVF$) can have egg and sperm cells examined for single-gene or chromosomal concerns before implantation.

Genes are the basic units of heredity determining physical and cognitive characteristics. They are composed of segments of DNA ($\text{deoxyribonucleic acid}$) and are woven into strands called chromosomes in the nucleus of body cells. In humans, each cell except the sperm and ovum contains $46$ chromosomes, consisting of $22$ pairs of autosomes and $1$ pair of sex chromosomes. Spermatozoa and ova carry only half the number ($23$ chromosomes). For every chromosome in the sperm, there is a homologous chromosome of similar size, shape, and function in the ovum.

Because genes are located at fixed positions on chromosomes, two like genes, known as alleles, for every trait are represented in the ovum and sperm on autosomes. The sex chromosomes determine gender: a zygote with two $X$ chromosomes ($46XX$) is female, while a zygote with one $X$ and one smaller $Y$ chromosome ($46XY$) is male. A person’s phenotype is their outward appearance or gene expression, while the genotype is their actual gene composition. Predicting genotype from phenotype is impossible. The human genome consists of the complete set of genes, approximately $50,000$ to $100,000$.

Mendelian Inheritance Patterns: Dominant and Recessive Disorders

A person with two identical genes for a trait (e.g., two healthy genes from both parents) is homozygous. If the genes differ (one healthy and one unhealthy), the person is heterozygous. Dominant genes are expressed in preference to recessive genes when paired. An individual with two homozygous genes for a dominant trait is homozygous dominant; two genes for a recessive trait make them homozygous recessive.

Autosomal dominant disorders occur when a person has two unhealthy genes (homozygous dominant) or is heterozygous, where the disease gene is stronger than the healthy recessive gene. If a heterozygous person for an autosomal dominant trait mates with a person free of the trait, there is a $50\%$ chance the child will have the disorder and a $50\%$ chance the child will be disease and carrier-free. If two heterozygous people mate (though rare), there is only a $25\%$ chance of the child being disease-free, a $50\%$ chance of the child having the disorder, and a $25\%$ chance of the child being homozygous dominant, which is often incompatible with life. Characteristics of this inheritance include vertical transmission (one parent usually has the disorder), the sex of the individual does not affect inheritance, and there is usually a history of the disorder in other members.

Autosomal recessive inheritance typically involves biochemical or enzymatic diseases that only occur if two disease genes are present. Examples include cystic fibrosis, adrenogenital syndrome, albinism, Tay-Sachs disease, galactosemia, phenylketonuria, limb-girdle muscular dystrophy, and Rh factor incompatibility. Characteristics include: parents are usually clinically free of the disorder, the sex of the affected individual is unimportant, the family history is often negative (horizontal transmission pattern), and there may be a known common ancestor between parents.

Sex-Linked and Multifactorial Inheritance Paradigms

X-linked dominant inheritance involves genes located on and transmitted by the female $X$ chromosome. If the gene is dominant, symptoms manifest if only one affected $X$ is present. Key features: all individuals with the gene are affected, all female children of affected men are affected, all male children of affected men are unaffected, and the trait appears in every generation. For homozygous affected women, all children are affected; for heterozygous women, there is a $50\%$ chance of passing it to children.

X-linked recessive inheritance is more common. Females with one affected gene are typically carriers (heterozygous) because the normal $X$ gene blocks expression. However, males manifestation the disease if they receive the affected $X$ from their mother because they have only one $X$ chromosome. Examples include Hemophilia A, Christmas disease ($\text{blood-factor deficiencies}$), color blindness, Duchenne ($\text{pseudohypertrophic}$) muscular dystrophy, and fragile X syndrome ($\text{a cognitive challenge syndrome}$). If a carrier mother and disease-free father mate, there is a $50\%$ chance a son will have the disease and a $50\%$ chance a daughter will be a carrier. If an affected father mates with a disease-free mother, $100\%$ of daughters will be carriers, and $0\%$ of sons will be affected. Family genograms show only males with the disorder, potential history of female infant deaths, and unaffected sons of affected men.

Multifactorial or polygenic inheritance applies to disorders like heart disease, diabetes, pyloric stenosis, cleft lip and palate, neural tube disorders, hypertension, and mental illness. These result from multiple gene combinations often combined with environmental factors. They do not follow Mendelian laws and are unpredictable. Some have a predisposition toward one sex (e.g., cleft palate occurs more often in girls).

Imprinting refers to the differential expression of genetic material depending on whether it was inherited from the male or female parent, allowing researchers to identify the parental origin of chromosomal material.

Chromosomal Abnormalities and Cytogenetic Disorders

Chromosomal abnormalities result from faults in the number or structure of chromosomes, leading to missing or distorted genes. A karyotype is the photographed arrangement of chromosomes. Identification is done via karyotyping or fluorescent in situ hybridization ($FISH$).

Nondisjunction abnormalities occur during meiosis, where cell division should result in a haploid number of $23$ chromosomes. If division is uneven, a gamete may have $24$ or $22$ chromosomes. Fusion with a normal gamete results in a zygote with $47$ or $45$ chromosomes. A count of $45$ is generally incompatible with life and results in miscarriage.

Deletion abnormalities occur when part of a chromosome breaks during cell division. Translocation abnormalities involve a misplaced chromosome attached to another (e.g., chromosome $21$ attached to $14$ or $15$). A balanced translocation carrier has $46$ chromosomes and appears normal, but if they pass the extra material to a child, it results in an unbalanced translocation syndrome (e.g., a form of Down syndrome) with a total of $47$ chromosomes.

Mosaicism occurs when nondisjunction happens after fertilization during mitotic division, leading to different cell counts in different body tissues. Isochromosomes result from horizontal rather than vertical division of a chromosome, leading to mismatched long and short arms.

Genetic Counseling: Purpose, Process, and Ethical Considerations

Genetic counseling provides accurate information about inheritance, reassures parents, and allows for informed reproductive choices. It can alleviate guilt by clarifying if a disorder was a chance occurrence rather than inherited. Confidentiality is essential, as genetic information could damage reputations or careers. Providers cannot alert family members without consent from the person seeking assessment. Counseling may reveal sensitive information, such as non-paternity or adoption, which the seeker has the right to keep private.

Ideally, counseling occurs before a first pregnancy or after the birth of a child with a disorder once the initial grief has subsided. Couples who benefit from referral include those with a child with a congenital disorder or inborn error of metabolism, those with close relatives with genetic disorders, balanced translocation carriers, individuals with chromosomal disorders, and consanguineous couples (closely related individuals). Siblings share $50\%$ of genes, while first cousins share $12\%$. Advanced parental age (women over $35$ years and men over $55$ years) increases risk for Down syndrome. Certain ethnic groups are also at risk: Mediterranean descent for thalassemia and Chinese ancestry for glucose-6-phosphate dehydrogenase ($G6PD$) deficiency.

Nursing Responsibilities and Genetic Assessment

Nurses assess for symptoms, offer support, and assist with testing procedures. This includes explaining procedures and screening tests, supporting couples during wait times, and assisting in values clarification and decision-making. Assessment involves obtaining a three-generation family history including half-siblings and miscarriages. Nurses must document parental age, consanguinity, and ethnic background.

Physical assessment includes inspecting body areas like the space between eyes, ear contour, number of digits, and presence of webbing. Dermatoglyphics involves studying skin surface markings, such as abnormal palmar creases or fingerprints. Hair whorls and coloring also provide clues. Newborns with multiple congenital anomalies, those born before $35$ weeks, or those with siblings with chromosomal disorders require intense assessment.

Procedures and Diagnostic Testing for Genetic Evaluation

Karyotyping uses peripheral blood or buccal membrane scrapings, staining cells during metaphase. $FISH$ allows for immediate results within $1$ day. Maternal Serum Screening for Alpha-fetoprotein ($AFP$) is peak at $13$ to $32$ weeks, usually tested at the $15^{th}$ week. While it has a $30\%$ false-positive rate, a "triple study" (including $AFP$, $estriol$, and $hCG$) improves accuracy.

Chorionic Villi Sampling ($CVS$) involves analysis of placental cells, typically done at $8$ to $10$ weeks. It carries a less than $1\%$ risk of bleeding or pregnancy loss. Rh-negative women require Rh immune globulin post-procedure. Amniocentesis involves withdrawing about $20\,mL$ of amniotic fluid at the $14^{th}$ to $16^{th}$ week for karyotyping and $AFP$ analysis when fluid levels reach $200\,mL$.

Percutaneous Umbilical Blood Sampling ($PUBS$), or cordocentesis, removes blood from the fetal umbilical cord at $17$ weeks for rapid karyotyping. Fetal imaging via ultrasound and $MRI$ identifies structural disorders. Fetoscopy allows visual inspection through a fiberoptic scope for gross abnormalities or surgery. Preimplantation Diagnosis is used in $IVF$ to study the ovum before implantation, and lavage may be used in the future for naturally fertilized ova.