IBCLC Practice Exam 2025 – Complete Preparation Guide

Lactogenesis I typically begins around 16 weeks of gestation. This phase is characterized by the initial stages of milk production, where the mammary glands start to develop the capacity to produce milk in response to hormonal changes that occur during pregnancy. During lactogenesis I, colostrum, the first form of milk rich in antibodies, begins to be produced and stored in the breasts.

This phase is critical because it sets the stage for lactogenesis II, which occurs after delivery and involves the actual secretion of milk in response to physiological stimuli like suckling. It is important to recognize that while lactogenesis I starts around 16 weeks, the production of mature milk typically begins in full after birth with the hormonal changes triggered by the baby’s first feeds. Understanding the timing of these developmental stages is crucial for lactation consultants in supporting breastfeeding mothers effectively.