Which pattern in maternal serum testing is associated with Down syndrome?

• A. Decreased AFP, decreased estriol, increased gonadotrophin
• B. Increased AFP, increased estriol, decreased gonadotrophin
• C. Decreased AFP, increased estriol, increased gonadotrophin
• D. Increased AFP, decreased estriol, decreased gonadotrophin

Answer: (A)

The key idea is the typical pattern seen in the second-trimester maternal serum screen for Down syndrome. In trisomy 21, the markers shift in a characteristic way: alpha-fetoprotein (AFP) tends to be lower than normal, unconjugated estriol (uE3) is also lower, and human chorionic gonadotropin (hCG) is higher. This reflects fetal and placental changes associated with trisomy 21, where reduced fetal production of AFP and estriol occurs alongside increased placental production of hCG. The option that shows decreased AFP, decreased estriol, and increased gonadotrophin matches this pattern, making it the best choice. The other patterns don’t align with Down syndrome because they imply opposite or different marker trends.