## **Core Concept**
The corpus luteum plays a critical role in the menstrual cycle and early pregnancy by producing **progesterone**, which is essential for preparing and maintaining the endometrium. After ovulation, the corpus luteum forms from the ruptured follicle in the ovary and is responsible for the production of progesterone during the luteal phase. In early pregnancy, the corpus luteum continues to produce progesterone until the placenta takes over this function.

## **Why the Correct Answer is Right**
The correct answer, , indicates that the corpus luteum supports the endometrium in pregnancy until about the **8th to 10th week** of gestation. During this period, the corpus luteum continues to produce progesterone, which is crucial for the growth and maintenance of the endometrium, supporting the implantation and early development of the embryo. After this period, the **placenta** develops and becomes the primary source of progesterone, taking over from the corpus luteum. This transition is vital for the continuation of pregnancy.

## **Why Each Wrong Option is Incorrect**
- **Option A:** . This option suggests a much earlier timeframe than accurate. The corpus luteum's role does extend beyond ovulation but saying it supports the endometrium only up to ovulation is incorrect because its role extends into early pregnancy.
- **Option B:** . This timeframe is too early for the transition from corpus luteum to placenta. While it's true that by around 7 weeks the placenta starts to contribute significantly to progesterone production, the corpus luteum's support is generally considered necessary until about the 8th to 10th week.
- **Option D:** . This option suggests a much later timeframe than correct. By the 12th week, the placenta is well-established as the primary source of progesterone, making the corpus luteum less critical.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the corpus luteum's role in supporting early pregnancy through progesterone production is **crucial until about the 8th to 10th week**, after which the placenta takes over. This transition is critical for the maintenance of pregnancy. A failure in this transition can lead to **miscarriage** due to inadequate progesterone levels.

## **Correct Answer:** . 10 weeks.