A primigravida in 2nd trimester became positive for toxoplasmosis. Veical transmission of toxoplasmosis MOST commonly occurs in which trimester?
**Core Concept**
Toxoplasmosis is a parasitic infection caused by *Toxoplasma gondii*, which can be transmitted from mother to fetus during pregnancy, leading to congenital toxoplasmosis. Vertical transmission of toxoplasmosis refers to the transmission of the parasite from mother to fetus.
**Why the Correct Answer is Right**
Vertical transmission of toxoplasmosis can occur at any time during pregnancy. However, the risk of transmission is highest during the 2nd trimester due to the fact that the placenta is fully developed and the parasite can cross the placental barrier more easily. Additionally, the fetus's immune system is not yet developed enough to effectively fight off the infection during this period.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because vertical transmission of toxoplasmosis is not most common in the 1st trimester, as the placenta is still developing and the risk of transmission is lower.
* **Option B:** This option is incorrect because vertical transmission of toxoplasmosis is not most common in the 3rd trimester, as the fetus's immune system is more developed and can fight off the infection to some extent.
* **Option D:** This option is incorrect because vertical transmission of toxoplasmosis can occur at any time during pregnancy, but it is not most common in the 1st trimester.
**Clinical Pearl / High-Yield Fact**
Toxoplasmosis can be prevented or reduced in risk by taking measures such as avoiding undercooked meat, washing hands thoroughly after handling cat litter, and avoiding raw or unpasteurized dairy products.
**Correct Answer:** C.