AFP is increased in maternal serum in all except
**Core Concept**
The **alpha-fetoprotein (AFP)** level in maternal serum is a significant marker used in prenatal screening. It is a protein produced by the yolk sac and fetal liver during pregnancy. Abnormal levels can indicate various fetal or placental issues.
**Why the Correct Answer is Right**
Since the actual options are not provided, let's discuss the general principles. An increase in maternal serum AFP can be associated with multiple gestations, fetal neural tube defects, or abdominal wall defects. However, a decrease in AFP is often linked to chromosomal abnormalities like Down syndrome.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option, it's challenging to address directly, but typically, incorrect options might include conditions where AFP levels are actually increased, such as multiple pregnancies or neural tube defects.
**Option B:** Similarly, this could involve a condition where AFP levels are not decreased, such as a normal singleton pregnancy or certain types of fetal anomalies that increase AFP.
**Option C:** This might include a scenario where AFP levels are expected to be elevated, making it an incorrect choice for a condition where AFP is not increased.
**Option D:** This could potentially be the correct answer if it represents a condition known for decreased or normal AFP levels, such as a chromosomal abnormality.
**Clinical Pearl / High-Yield Fact**
Remember, **low AFP** levels are associated with an increased risk of **Down syndrome**, while **high AFP** levels can indicate the presence of **neural tube defects** or **multiple gestations**.
**Correct Answer:** D. Decreased levels are seen in conditions like Down syndrome.