A 24-year-old woman has had three first-trimester spontaneous abortions. Which of the following statements concerning chromosomal aberrations in abortions is true?
- 45,X is more prevalent in chromosomally abnormal term babies than in abortus products
- Approximately 20% of first-trimester spontaneous abortions have chromosomal abnormalities
- Trisomy 21 is the most common trisomy in abortuses
- Despite the relatively high frequency of Down syndrome at term, most Down fetuses abort spontaneously
- Stillbirths have twice the incidence of chromosomal abnormalities as live births
the answer is below…
The United States Medical Licensing Examination, or USMLE for short, is a three-part licensing examination that is required in order to receive a license to practice medicine within the United States.
The USMLE assesses a physician’s ability to apply knowledge, concepts, and principles, and to determine fundamental patient-centered skills that are important in health and disease and that constitute the basis of safe and effective patient care.Examination committees composed of medical educators and clinicians from across the United States and its territories prepare the examination materials each year.
This exam is designed by the Federation of State Medical Boards and the National Board of Medical Examiners to determine whether or not an individual understands and can apply the knowledge necessary to practice medicine safely and intelligently.
The USMLE is actually comprised of three different exams that are referred to as steps, which examine the individual’s knowledge of specific topics related to the field of medicine such as basic science, medical knowledge, medical skills, clinical science, and the application of all of these skills and areas of knowledge in the medical field.
All three steps of the USMLE include a series of computerized multiple-choice questions, but the format of the exam and the information covered in each multiple-choice section is different for each step of the USMLE. The USMLE Step II also has a clinical skills portion that examines an individual’s ability to work with real patients and the USMLE Step III has a computerized patient simulation portion in addition to the multiple-choice section of the exam. In order for an individual to receive a license to practice medicine, the individual must pass all three steps of the USMLE.
The answer is d, Despite the relatively high frequency of Down syndrome at term, most Down fetuses abort spontaneously.[2-3]
Chromosomal abnormalities are found in approximately 50% of spontaneous abortions, 5% of stillbirths, and 0.5% of live-born babies. In spontaneous losses, trisomy 16 is the most common trisomy, with 45,X the most common single abnormality found. At term, trisomy 16 is never seen, and 45,X is seen in approximately 1 in 2,000 births. It is estimated that 99% of 45,X and 75% of trisomy 21 conceptuses are lost before term.