Understanding Down Syndrome Risks Based on Maternal Age and Genetic Factors

In genetics clinic, you are counseling five pregnant who inquire about their risk for having a Down syndrome fetus. What are their risks and why?a. a 23 year old mother of a previous trisomy 21 childb. a 41 year old mother of a previously trisomy 21 childc. a 27 year old woman whose niece has Down syndromed. a carrier of a 14;21 Robertsonian translocatione. a woman whose husband is a carrier of a 14;21 Robertsonian translocation

The correct answer is A

a. The risk for a 23-year-old mother with a previous trisomy 21 child to have another child with Down syndrome is relatively low. The recurrence risk for a couple with one previous child with Down syndrome is estimated to be around 1% to 2%. The risk factors for having a child with Down syndrome increase with maternal age, but at 23 years old, the risk is generally considered to be in the lower range.

b. The risk for a 41-year-old mother with a previous trisomy 21 child to have another child with Down syndrome is significantly higher compared to a younger mother. Maternal age is one of the most significant factors influencing the risk of having a child with Down syndrome. At age 41, the risk is around 1 in 100.

c. The risk for a 27-year-old woman whose niece has Down syndrome to have a child with Down syndrome herself is low. The fact that her niece has Down syndrome does not directly increase her risk significantly. The majority of cases of Down syndrome occur sporadically, meaning they happen by chance and are not inherited. The background risk for a 27-year-old woman is around 1 in 1,000.

d. A carrier of a 14;21 Robertsonian translocation has an increased risk of having a child with Down syndrome. In this translocation, a piece of chromosome 21 attaches to another chromosome, usually chromosome 14. If a carrier of this translocation has a child, there is a 50% chance that the child will inherit the translocation and be at increased risk for Down syndrome. The actual risk for Down syndrome varies depending on the specifics of the translocation and the individual’s genetic background.

e. As for a woman whose husband is a carrier of a 14;21 Robertsonian translocation, the risk of having a child with Down syndrome is also increased in this case. The risk depends on whether or not the woman is also a carrier of the translocation. If she is not a carrier, the risk would be lower. However, if she is a carrier, the risk for having a child with Down syndrome would be higher.

It is worth noting that these risks are provided as general information and individual counseling by a genetic specialist is always recommended to get a more accurate assessment based on personal and family medical histories, as well as detailed genetic testing if applicable.

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