USA Biology Olympiad (USABO) Practice Exam

During the first 6 to 8 weeks of gestation, the main source of estrogen and progesterone is the:

1. Placenta

2. Follicle cells

3. Corpus luteum

4. Hypothalamus

The correct answer is: Corpus luteum

During the initial stages of gestation, specifically the first 6 to 8 weeks, the corpus luteum plays a crucial role as the primary source of the hormones estrogen and progesterone. After ovulation, the ruptured follicle transforms into the corpus luteum, which produces these hormones essential for maintaining the uterine lining and supporting early pregnancy. The presence of adequate levels of estrogen and progesterone is vital for sustaining the pregnancy during this early period, as they help inhibit further ovulation and prevent menstruation. Following this early period, hormonal support shifts from the corpus luteum to the placenta, which eventually takes over the production of these hormones around the end of the first trimester. Understanding the timing and functions of these hormonal sources is important for comprehending early pregnancy physiology and the transition of hormonal roles as pregnancy progresses.