Nokea
A couple has given birth to their first child, a boy with a recessive disorder. The genetic counselor tells them that the risk of recurrence is one in four. Which statement is a correct interpretation of this information?
- A. The risk factor remains the same for each pregnancy.
- B. The risk factor will change when they have a second child.
- C. Because the parents have one affected child, the next three children should be unaffected.
- D. Because the parents have one affected child, the next child is four times more likely to be affected.
Correct Answer: A
Rationale: Each pregnancy has the same risks for an affected child. Because an odds ratio reflects the risk, this does not change over time. The statement by the genetic counselor refers to a probability. This does not change over time. The statement Because the parents have one affected child, the next child is four times more likely to be affected does not reflect autosomal recessive inheritance.
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Which is a sex chromosome abnormality that is caused by the presence of one or more additional X chromosomes in a male?
- A. Turner
- B. Triple X
- C. Klinefelter
- D. Trisomy 13
Correct Answer: C
Rationale: Klinefelter syndrome is characterized by one or more additional X chromosomes. These individuals are tall with male secondary sexual characteristics that may be deficient, and they may be learning disabled. An absence of an X chromosome results in Turner syndrome. Triple X and trisomy 13 are not abnormalities that involve one or more additional X chromosomes in a male (Klinefelter syndrome).
Chromosome analysis of the fetus is usually accomplished through the testing of which?
- A. Fetal serum
- B. Maternal urine
- C. Amniotic fluid
- D. Maternal serum
Correct Answer: C
Rationale: Amniocentesis is the most common method to retrieve fetal cells for chromosome analysis. Viable fetal cells are sloughed off into the amniotic fluid, and when a sample is taken, they can be cultured and analyzed. It is difficult to obtain a sample of the fetal blood. It is a high-risk situation for the fetus. Fetal cells are not present in the maternal urine or blood.
A couple expecting their first child has a positive family history for several congenital defects and disorders. The couple tells the nurse that they are opposed to abortion for religious reasons. Which should the nurse consider when counseling the couple?
- A. The couple should be encouraged to have recommended diagnostic testing.
- B. The couple needs counseling regarding advantages and disadvantages of pregnancy termination.
- C. Diagnostic testing is required by law in this situation.
- D. Diagnostic testing is of limited value if termination of pregnancy is not an option.
Correct Answer: A
Rationale: The benefits of prenatal diagnostic testing extend beyond decisions concerning abortion. If the child has congenital disorders, decisions can be made about fetal surgery if indicated. In addition, if the child is expected to require neonatal intensive care at birth, the mother is encouraged to deliver at a level III neonatal center. The couple is counseled about the advantages and disadvantages of prenatal diagnosis, not pregnancy termination, although the family cannot be forced to have prenatal testing. The information gives the parents time to grieve and plan for their child if congenital disorders are present. If the child is free of defects, then the parents are relieved of a major worry.
Which is a birth defect or disorder that occurs as a new case in a family and is not inherited?
- A. Sporadic
- B. Polygenic
- C. Monosomy
- D. Association
Correct Answer: A
Rationale: Sporadic describes a birth defect previously unidentified in a family. It is not inherited. Polygenic inheritance involves the inheritance of many genes at separate loci whose combined effects produce a given phenotype. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. A nonrandom cluster of malformations without a specific cause is an association.
A woman, age 43 years, is 6 weeks pregnant. It is important that she be informed of which?
- A. The need for a therapeutic abortion
- B. Increased risk for Down syndrome
- C. Increased risk for Turner syndrome
- D. The need for an immediate amniocentesis
Correct Answer: B
Rationale: Women who are older than age 35 years at the birth of a single child or 31 years at the birth of twins are advised to have prenatal diagnosis. The risk of having a child with Down syndrome increases with maternal age. There is no indication of a need for a therapeutic abortion at this stage. Turner syndrome is not associated with advanced maternal age. Amniocentesis cannot be done at a gestational age of 6 weeks.