## **Core Concept**
Human chorionic gonadotropin (hCG) is a hormone produced during pregnancy that is made by the developing embryo after conception and later by the placental component **syncytiotrophoblast**. It plays a critical role in maintaining the corpus luteum, ensuring continued production of **progesterone** during early pregnancy. The levels of hCG can be detected in blood and urine and serve as a marker for pregnancy.

## **Why the Correct Answer is Right**
The levels of maternal hCG increase significantly after implantation of the embryo into the uterine wall. These levels peak around the **8-10th week of gestation** (or approximately 6-8 weeks post-conception) in a normal pregnancy. This peak is crucial for maintaining the **corpus luteum**, which in turn continues to produce **progesterone** until the placenta takes over this function later in pregnancy. The hCG levels then decline as the **syncytiotrophoblast** matures and produces more **progesterone** and **estrogen**.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests an earlier peak, which does not align with the known physiology of hCG levels during pregnancy. hCG levels do start rising early but peak later.
- **Option B:** This option suggests a later peak than what is typically observed. While hCG does play a role throughout early pregnancy, its peak occurs before the end of the first trimester.
- **Option D:** This option suggests a much later peak than what is observed. By the 20th week, hCG levels have usually decreased significantly from their peak.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that **hCG levels typically peak around 8-10 weeks of gestation** and then decline. Abnormal levels of hCG can be associated with various pregnancy-related complications, such as **ectopic pregnancy** or **miscarriage**. Clinicians use hCG levels as a tool for monitoring the health and progression of early pregnancy.

## **Correct Answer:** C. 8-10 weeks.