Certified Breastfeeding Counselor (CBC) 2025 – 400 Free Practice Questions to Pass the Exam

Estrogen is the primary hormone responsible for initiating the development of the ductal system in the breast during menstruation. This hormone plays a crucial role in the hormonal changes that occur throughout the menstrual cycle. During the follicular phase, which includes menstruation, estrogen levels rise, stimulating the proliferation of ductal epithelial cells in the breast. This process is essential for preparing the breast tissue for potential lactation should pregnancy occur.

Progesterone also contributes to breast development, but its primary role emerges later in the cycle and more prominently during pregnancy, where it promotes the development of lobular structures and prepares the breasts for milk production. Prolactin's main function is in milk production after childbirth rather than ductal development, while oxytocin is involved in milk ejection and has no direct role in ductal system development during menstruation. Thus, the focus on estrogen's role clarifies why it is the correct answer for this particular question.