downs syndrome is caused by

HESI LPN

HESI Maternal Newborn

1. What causes Down's syndrome?

A. Alcohol abuse by the mother at the time of conception.
B. Sex-linked chromosomal abnormalities.
C. An extra chromosome on the 21st pair.
D. Drug abuse by the mother during pregnancy.

Correct answer: C

Rationale: Down's syndrome, also known as trisomy 21, is caused by the presence of an extra chromosome on the 21st pair. Choice A is incorrect as alcohol abuse is not the cause of Down's syndrome. Choice B is incorrect because Down's syndrome is not related to sex-linked chromosomal abnormalities. Choice D is also incorrect as drug abuse by the mother during pregnancy is not the cause of Down's syndrome.

2. Why is a client with gestational diabetes being scheduled for an amniocentesis when the fetus has an estimated weight of eight pounds (3629 grams) at 36 weeks gestation? What information is the amniocentesis seeking to obtain?

A. Presence of a neural tube defect.
B. Chromosomal abnormalities.
C. Gender of the fetus.
D. Fetal lung maturity.

Correct answer: D

Rationale: An amniocentesis in this scenario is most likely being performed to assess fetal lung maturity. This is necessary when considering early delivery due to macrosomia (large fetal size), which is a common concern in gestational diabetes. Evaluating fetal lung maturity is crucial to determine if the fetus's lungs are developed enough to support breathing independently outside the womb. The presence of a neural tube defect and chromosomal abnormalities are not typically assessed through amniocentesis in this situation, and determining the gender of the fetus is not the primary purpose of the procedure here.

3. In the context of an average ejaculation, which of the following statements is true about sperm?

A. The average count of sperm in the ejaculate is 2.5 billion.
B. Sperm in the ejaculate find the ovum by following the current of the fluid coming from the cervix.
C. Only 1 in 1,000 sperm in the ejaculate will ever approach an ovum.
D. Most of the sperm in the ejaculate move about in a random pattern in the vagina.

Correct answer: C

Rationale: Out of millions of sperm released during ejaculation, only a small fraction, about 1 in 1,000, will approach the ovum. This statement is true as sperm face many obstacles and challenges on their journey to reach and fertilize an ovum. Choice A is incorrect because the average count of sperm in an ejaculate is typically in the millions, not billions. Choice B is incorrect as sperm do not find the ovum by following the current of fluid; they navigate using other mechanisms. Choice D is incorrect because while some sperm may move randomly in the vagina, the ones that approach the ovum do so through a more purposeful and directed movement.

4. A client at 34 weeks gestation comes to the birthing center complaining of vaginal bleeding that began one hour ago. The nurse's assessment reveals approximately 30ML of bright red vaginal bleeding, fetal heart rate of 130 - 140 beats per minute, no contractions, and no complaints of pain. What is the most likely cause of this client's bleeding?

A. Abruptio Placenta
B. Placenta Previa
C. Normal bloody show indicating induction of labor
D. A ruptured blood vessel in the vaginal vault

Correct answer: B

Rationale: Placenta previa, a condition where the placenta covers the cervix, can cause painless, bright red vaginal bleeding in the third trimester. In this scenario, the absence of contractions and pain, along with the presence of significant bright red bleeding, is more indicative of placenta previa rather than abruptio placenta or a ruptured vessel. A normal bloody show typically occurs closer to the onset of labor and is not associated with the amount of bleeding described in the question.

5. Is Duchenne muscular dystrophy a sex-linked abnormality?

A. TRUE
B. FALSE
C. Sometimes
D. Always

Correct answer: A

Rationale: The correct answer is A: TRUE. Duchenne muscular dystrophy is an X-linked recessive disorder, primarily affecting males. This is due to the inheritance of the mutated gene on the X chromosome. Choices B, C, and D are incorrect because Duchenne muscular dystrophy is specifically classified as a sex-linked disorder affecting males due to the inheritance pattern.