An HIV positive, 36 years old female on ART needs counseling. Which of the following 1st trimester markers of Down syndrome would be affected by HIV:
**Core Concept**
The question is testing the understanding of how HIV infection affects the levels of certain pregnancy-related markers, specifically those associated with Down syndrome. The underlying principle involves the interaction between HIV and the placental production of these markers.
**Why the Correct Answer is Right**
HIV infection is known to cause inflammation and immune activation in the placenta, leading to changes in the levels of various pregnancy-related markers. One such marker is **free beta-human chorionic gonadotropin (β-hCG)**, which is often used in the first trimester to screen for Down syndrome. However, HIV infection can cause an increase in the levels of **total β-hCG**, but not **free β-hCG**, due to the binding of β-hCG to the gp41 glycoprotein on the surface of HIV-infected cells.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the question, as it does not specify a particular marker associated with Down syndrome.
* **Option B:** This option is incorrect because **alpha-fetoprotein (AFP)** is not typically affected by HIV infection in the first trimester.
* **Option C:** This option is incorrect because **inhibin A** is not a commonly used marker for Down syndrome screening in the first trimester.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that HIV infection can cause changes in the levels of various pregnancy-related markers, which can lead to false-positive or false-negative results in screening tests for Down syndrome. Healthcare providers should be aware of these changes to provide accurate counseling to patients.
**Correct Answer:** B.