In triple screening test for Down’s syndrome during pregnancy all of the following are included except.
**Core Concept**
The triple screening test, also known as the triple marker test, is a prenatal test used to screen for Down syndrome (Trisomy 21) and other chromosomal abnormalities during pregnancy. It measures the levels of three substances in the maternal blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol (E3).
**Why the Correct Answer is Right**
The triple screening test includes AFP, hCG, and estriol to estimate the risk of Down syndrome. AFP is a protein produced by the fetus, hCG is a hormone produced by the placenta, and estriol is a form of estrogen produced by the placenta and fetus. The levels of these substances are measured to calculate a risk score.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because AFP is indeed one of the substances measured in the triple screening test.
* **Option B:** Incorrect because hCG is also one of the substances measured in the triple screening test.
* **Option C:** Incorrect because estriol is indeed one of the substances measured in the triple screening test.
**Clinical Pearl / High-Yield Fact**
The triple screening test is a screening test, not a diagnostic test, and it should not be used to make a definitive diagnosis. A positive result indicates an increased risk, and further testing, such as amniocentesis or chorionic villus sampling, may be recommended.
**Correct Answer: D**