International Board of Certified Lactation Consultant (IBCLC) Practice Exam

During which phase of lactation does secretory differentiation occur?

1. Lactogenesis I

2. Lactogenesis II

3. Galactopoiesis

4. Weaning

The correct answer is: Lactogenesis I

Secretory differentiation occurs during Lactogenesis I. This phase is crucial as it involves the preparation of the mammary glands for milk production. During Lactogenesis I, which typically begins during the second trimester of pregnancy and continues through the first few days postpartum, the mammary epithelial cells undergo significant changes. These changes include the increase in the number and type of cells, the development of the milk-producing alveoli, and the production of colostrum, which is the first milk produced. The hormonal environment, particularly the influence of estrogen and progesterone, plays a vital role in this differentiating process. Lactogenesis II, on the other hand, marks the onset of copious milk production, primarily triggered by the drop in progesterone levels after delivery. Galactopoiesis refers to the maintenance of established milk production in the months following Lactogenesis II and is influenced by infant suckling and hormonal signals. Weaning describes the process of reducing or stopping breastfeeding and does not pertain to the differentiation phase of lactation but rather to the end of the lactation cycle. Understanding these phases helps in recognizing how profound hormonal and physiological changes support breastfeeding and lactation.