system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 3500-g (7 lb 11 oz) healthy female newborn is delivered at 38 weeks' gestation. Chorionic villus sampling (CVS) in the first trimester showed a trisomy of chromosome 21 but the pregnancy was otherwise uncomplicated. Physical examination of the newborn is normal. Chromosomal analysis at birth shows a 46, XX karyotype. Which of the following is the most likely explanation for the prenatal chromosomal abnormality?
assistant
Placental mosaicism