Download Genetic Issues for Perinatal Nurses, 3 rd Edition

Genetic Issues for
Perinatal Nurses, 3rd
Edition
Judith A. Lewis, PhD, RN, WHNP-BC, FAAN
The Human Genome Project
• Began in 1990 as an international
consortium, including the NIH and
Department of Energy
• Human genome sequencing announced in
2003, opening a new era in understanding
health and illness
• Continues to address ethical, legal and
social implications
• www.genome.gov
© 2010 March of Dimes Foundation
Relevance to Nursing
• All nurses must be competent in genetics
and genomics.
• The Consensus Panel on Genetic/Genomic
Nursing Competencies (2006) developed
essential genetic/genomic nursing
competencies and curricula guidelines.
• Several nursing organizations have
published practice guidelines related to
genetics and genomics.
© 2010 March of Dimes Foundation
Terminology
• Genetics— The study of individual genes,
including the impact of individual genes on
relatively rare disorders.
• Genomics—The study of all genes in the
human genome, including the study of
interactions among genes and interactions
between genes and the environment
(Guttmacher & Collins, 2002)
© 2010 March of Dimes Foundation
Terminology
(Continued)
• Genetic counseling—A communication
process that deals with human problems
associated with the occurrence, or the
risk of occurrence, of a genetic disorder in
a family (American Society of Human Genetics,
1975).
• Genetic evaluation—Broader than genetic
counseling; includes information
gathering, information sharing and valueneutral counseling.
© 2010 March of Dimes Foundation
Terminology
(Continued)
• Informed consent—The process of
communication between a client and a
health care provider that results in the
client’s authorization or agreement to
undergo a specific medical intervention
(American Medical Association, 2009).
© 2010 March of Dimes Foundation
Genetics Health Professionals
• Medical geneticists—MD or PhD degree
with advanced training in genetics
• Physicians—Certification available from
the American Board of Medical Genetics
• Genetic counselors—Master’s degree;
certification available from the American
Board of Genetic Counseling
© 2010 March of Dimes Foundation
DNA Structure and Replication
• DNA provides the codes for proteins. It is
a double helix made of two strands held
together with chemical bonds.
• DNA replicates by undoing the bonds and
creating a complementary strand.
• As the strands separate, one serves as a
template for messenger RNA (mRNA), the
structure that carries information stored
on DNA to where proteins are synthesized.
© 2010 March of Dimes Foundation
DNA Molecule
© 2010 March of Dimes Foundation
(National Cancer Institute, 1982)
Genes
• The human genome consists of
approximately 30,000 genes (U.S.
Department of Energy, Office of Science, 2009).
• Mutations are alterations in the genetic
code. They occur rarely.
• Differences that occur more frequently
are called polymorphisms.
© 2010 March of Dimes Foundation
Chromosomes
• Genes are organized in a linear fashion
along chromosomes.
• Chromosome pairs 1 through 22 are called
autosomes.
• The 23rd pair contains the sex
chromosomes: XX in females and XY in
males.
© 2010 March of Dimes Foundation
Chromosomes
(Continued)
Normal male karyotype (National Cancer Institute, 1997)
© 2010 March of Dimes Foundation
Chromosomes
(Continued)
• When the alleles on a pair of chromosomes
are identical, the person is called
homozygous for the trait.
• If the alleles are different, then the
person is heterozygous for the trait.
© 2010 March of Dimes Foundation
Chromosomes
(Continued)
• Before a somatic (non-gamete) cell
divides, the chromosomes duplicate so
that each resulting cell has the original
number of 46 chromosomes; this type of
cell division is called mitosis.
• Meiosis is a two-step cell-division process
that occurs in cells that generate sperm
and egg cells.
© 2010 March of Dimes Foundation
Chromosomes
(Continued)
• During meiosis, crossing over can allow
homologous chromosomes to exchange
sections of genetic material; this is called
recombination.
• During meiosis, a separation error can
cause:
• Monosomy (resulting zygote has one copy
of a chromosome)
• Trisomy (resulting zygote has three copies
of a chromosome)
© 2010 March of Dimes Foundation
Chromosomes
(Continued)
• Chromosomal abnormalities
• Structural—Chromosomal material can
break off and attach itself to another
chromosome, a process called
translocation.
• Deletions or duplications of genetic
material within a single chromosome
• Associated with advanced maternal age
© 2010 March of Dimes Foundation
Patterns of Inheritance
• Mendelian—Single-gene disorders caused
by mutations in a specific gene; can use
Mendel’s laws to predict the likelihood of
inheritance
• Non-Mendelian
• Multifactorial—Occur when genes and
environmental factors interact
© 2010 March of Dimes Foundation
Mendelian: Autosomal Dominant
• Only one allele is required to contain a
mutation.
• A parent has a 50-percent chance of
passing the mutation to each offspring.
• Examples
• Marfan syndrome
• Neurofibromatosis
• Huntington’s disease
© 2010 March of Dimes Foundation
Mendelian: Autosomal Recessive
• A mutation is present on both gene copies.
• Unaffected carriers can pass the mutation
through generations until a carrier mates
with another carrier and they have a child
with the condition.
• Chances that parents carry the same gene
mutations increase when they are related
through a common ancestor
(consanguinity).
© 2010 March of Dimes Foundation
Mendelian: Autosomal Recessive
(Continued)
• Examples
• Cystic fibrosis
• Factor V Leiden
• Tay-Sachs disease
© 2010 March of Dimes Foundation
Mendelian: X-Linked Recessive
• Genes are located on the X chromosome
• Most are recessive.
• Examples
• Hemophilia A
• Duchenne muscular dystrophy
• Red-green color blindness
© 2010 March of Dimes Foundation
Non-Mendelian:
Mitochondrial Inheritance
• Women with conditions caused by
mutations in mitochondrial DNA pass some
of the mutated DNA to their offspring.
• Conditions associated with mitochondrial
DNA mutations tend to involve skeletal
muscle, heart muscle and the brain.
© 2010 March of Dimes Foundation
Non-Mendelian: Anticipation
• Disorders that become more severe in
subsequent generations
• Examples
• Fragile X syndrome
• Myotonic dystrophy
• Huntington’s disease
© 2010 March of Dimes Foundation
Non-Mendelian:
Uniparental Disomy and Imprinting
• Uniparental disomy occurs when a child
inherits both alleles from a single parent.
• Imprinting occurs when genes from each
parent are not expressed equally.
© 2010 March of Dimes Foundation
Non-Mendelian:
Germline Mosaicism
• During early development, a mutation may
occur in a germline cell (egg or sperm) and
pass to descendents of that cell.
• Example: Osteogenesis imperfecta
© 2010 March of Dimes Foundation
Multifactorial
Examples
• Congenital heart defects
• Neural tube defects (NTDs)
• Diabetes
© 2010 March of Dimes Foundation
Family History
• The most powerful genetic tool available
• Includes a minimum of 3 generations
• Constructed as a pedigree that includes:
• Ethnicity, culture, religious background
• Living or deceased, age at death, cause of
death
• Physical, mental or developmental
conditions
© 2010 March of Dimes Foundation
Standard Pedigree Symbols
© 2010 March of Dimes Foundation
Prenatal Genetic Screening
• Identifies if a woman is at higher-thanaverage risk than other women of having a
baby with certain genetic conditions.
• Screeing tests include:
• Ultrasound
• Maternal serum screening
• Fetal nuchal translucency
• CF screening
© 2010 March of Dimes Foundation
Newborn Screening
• Newborn screening began in the United
States in 1961 with testing for PKU.
• State programs test approximately 4
million babies in this country each year;
an estimated 5,000 infants are diagnosed
with genetic disorders and birth defects
annually (Little & Lewis, 2008).
© 2010 March of Dimes Foundation
Dysmorphology Assessment
• Dysmorphology is the branch of clinical
genetics that studies congenital
abnormalities.
• Providers assess stillborn infants and
newborns with dysmorphic features to
determine the cause of the malformation
(Jones, 2008).
© 2010 March of Dimes Foundation
Implications of Genetic Screening
for Perinatal Nurses
• Nurses must be able to explain the
purpose of screening tests and provide
clients with information that allows them
to make informed decisions about whether
to accept or refuse tests as a routine part
of prenatal care.
• Women who receive positive results need
information and support as they decide on
a course of action.
© 2010 March of Dimes Foundation
Prenatal Genetic Diagnostic
Testing
• A diagnostic test actually diagnoses or
confirms a condition.
• Prenatal diagnostic tests include:
•
•
•
•
•
•
Ultrasound
Amniocentesis
Chorionic villus sampling
Carrier testing
Preimplantation diagnosis
Predictive testing
© 2010 March of Dimes Foundation
Newborn Genetic Diagnostic
Testing
• The earlier a diagnosis is made, the earlier
treatment can begin.
• In some cases, a diagnosis may lead to indepth genetics education and testing of
other family members.
© 2010 March of Dimes Foundation
Implications of Genetic Diagnostic
Testing for Perinatal Nurses
• For clients undergoing genetic diagnostic
testing, nurses need to provide safe,
effective and culturally appropriate care,
including patient education, support,
counseling and referral.
• Parents need to know the benefits, risks
and limitations of genetic diagnostic
testing.
© 2010 March of Dimes Foundation
Genetic Diagnostic Testing:
Benefits & Risks
Benefits
Testing can:
• Identify a fetus or individual
who is at risk for a genetic
condition
• Enable parents and providers
to consider prenatal
diagnostic options when a
fetus is at risk
• Relieve uncertainty
© 2010 March of Dimes Foundation
Risks
Test results may:
• Be hard for individuals and
families to handle.
• May negatively affect family
dynamics and interpersonal
relationships
Limitations of Genetic Diagnostic
Testing
• Cannot provide a definitive answer for
everyone at risk for an inherited
condition.
• Cannot always predict the likelihood of a
disease
• Cannot always predict the severity of a
disease
© 2010 March of Dimes Foundation
Genetic Diagnostic Testing
of Minors
• May be useful when the results can
contribute to immediate diagnosis and
treatment decisions.
• If cannot lead to treatment, should be
deferred until the child is old enough to
provide his own informed consent (AAP
Committee on Bioethics, 2001)
© 2010 March of Dimes Foundation
Pharmacogenomics
• Applies knowledge of the whole genome to
the use of pharmaceutical agents,
especially as they relate to therapeutic,
side and toxic effects (Lewis & Munro, 2010).
• By matching the therapeutic agent to a
person’s genetic composition, providers
may be able to tailor medication, enhance
results and minimize or eliminate
untoward effects.
© 2010 March of Dimes Foundation
Preventing Birth Defects:
Preconception Counseling
• The goal of preconception counseling is to
provide women with information to make
timely, informed decisions about future
reproduction (Moos, 2003).
• Includes:
•
•
•
•
Family history
Rubella immunity status
Treating chronic health conditions
Carrier testing
© 2010 March of Dimes Foundation
Preventing Birth Defects:
Folic Acid Supplementation
• Folic acid is essential early in pregnancy when
fetal tissues and organs are forming.
• All women of childbearing age should take 400
micrograms of folic acid daily from a multivitamin
or enriched foods (CDC, 2009).
• Women who have had a child with an NTD need 4
milligrams of folic acid daily at least 1 month
before conception and in the first few months
of pregnancy
© 2010 March of Dimes Foundation
(CDC, 2009).
Avoiding Teratogens
Type
Examples
Infectious disease
Rubella, CMV, toxoplasmosis
Medication
Lithium, phenytoin, valproic acid,
tetracycline, Accutane
Chemicals, radiation
Environmental
hazards
Other
© 2010 March of Dimes Foundation
Nicotine, alcohol
Managing Risk Factors
• Risk assessment includes fetal risk for birth
defects and risks to mother and other family
members for other conditions
• Providers should offer amniocentesis or CVS
to women who are carriers of genetic
conditions whose partners also are carriers.
• Genetic factors associated with PPROM may
help prevent preterm birth.
© 2010 March of Dimes Foundation
Essential Nursing Competencies
• Identifies minimal genetic and genomic
competences required of all nurses
• Includes professional responsibilities and
practice, including:
•
•
•
•
Nursing assessment
Identification
Referral activities
Education, care and support
(Consensus Panel on Genetics/Genomic Nursing
Competencies, 2006)
© 2010 March of Dimes Foundation
Specialized Genetics Nursing
Practice
• The ANA recognizes genetics as a nursing
specialty and has developed the scope and
standards of specialty practice for
professional nurses and APNs (ANA & ISONG,
2007).
• Nurses can be certified as a genetics
clinical nurse (GCN) or an APN in genetics
(APNG). APNs also can be certified as
genetic counselors.
© 2010 March of Dimes Foundation
Integrating Genetics into Nursing
Practice: Ethical Principles
• ANA’s (2001) Code of Ethics for Nurses with
Interpretive Statements guides nursing
practice.
• Nurses respect for parent choices by:
• Supporting parents’ decisions
• Ensuring privacy
• Respecting parents’ wishes about aspects of care
that they can control
• Including significant others at the infant’s birth
or death, if parents desire
© 2010 March of Dimes Foundation
Integrating Genetics into Nursing
Practice: Ethical Principles (Continued)
• Nurses demonstrate respect for parent
choices by:
• Supporting parents’ decisions
• Ensuring privacy
• Respecting parents’ wishes about aspects
of care that they can control
• Including significant others at the infant’s
birth or death, if parents desire
© 2010 March of Dimes Foundation
Genetics and the Future
• Gene therapy
• Human embryonic stem-cell research
• Risk profiling based on family history and
screening
© 2010 March of Dimes Foundation
The Danger of Genetic
Determinism: Eugenics
• Eugenics is the selective breeding of
humans.
• The eugenics movement in the United
States in the early 20th century included
sterilization and immigration laws against
people with undesirable traits.
• As we reap the benefits of genetic
science, we must use the knowledge of
genetics wisely.
© 2010 March of Dimes Foundation
Conclusion
Perinatal nurses must:
• Know about genetics and genomics to provide
care to women and infants who have, or who are
at risk for having, genetic conditions.
• Understand genetic screening and testing to help
women, couples and families acquire and
understand genetic information.
• Support parent care and treatment decisions.
• Know the ethical, legal and social implications of
genetic technologies.
© 2010 March of Dimes Foundation