What Happens to the Body During Lactogenesis

Lactogenesis is a big word, but it’s simpler than it sounds. If you distill it down, Lactogenesis is the process of developing the ability to secrete milk. To understand it a bit better, we’ve broken down the basics of what’s happening in each of the four stages, using a metaphor we all can relate to: driving a car. 

First, let’s learn the lingo: 

Estrogen: referred to as the female sex hormones, estrogen plays important roles in sexual and reproductive development and regulation. It is one of two main hormones (the other being prolactin) needed for lactation. Estrogen levels will naturally increase during pregnancy.

Prolactin: Sometimes called the ‘milk hormone,’ prolactin actually has more than 300 functions in the body, from reproductive and metabolic to the regulation of fluids and the immune system. Along with estrogen, it’s one of the two main hormones needed for lactation.

Oxytocin: stimulates contraction of the myoepithelial cells that surround the alveoli, causing the milk to be ejected into the ducts leading to the nipple. (source: Medscape)

Progesterone: interferes with prolactin binding to the receptors on the alveolar cells within the breast, thereby directly suppressing milk production. (source: Medscape)

Alveolar cells: Breast milk is produced by the mammary alveolar cells of the breast after childbirth. The mammary gland is a highly evolved skin gland (source: Science Direct)

Colostrum: a breast fluid produced in humans and other mammals before breast milk is released. This fluid contains high concentrations of sodium, chloride and other substances that serve as protection, like immunoglobulins and lactoferrin. 

Phase 1: Start the engine

Before you’re ready to hit the pavement, you have to start the engine. The same thing happens during the first phase of lactogenesis. This phase occurs during pregnancy, at approximately mid-pregnancy (around 16 weeks to be exact). 

There are a few tell-tale signs that you’ve entered lactogenesis. For one, your breasts will double in weight. There will also be increased blood flow and growth in lobules and alveoli (this is the progesterone effect). Lastly, there will be increased secretory activity. 

Phase 1 is really a ‘getting ready’ phase. Your body is setting certain processes into motion, so that you are ready to drive once you push the pedal. 

Phase 2: Begin to accelerate

Around day 4 postpartum, lactogenesis II kicks in. This is because giving birth triggers a hormonal shift in the body; the removal of the placenta at delivery also plays a role in accelerating this stage. There’s a rapid drop in progesterone, as well as elevated levels of prolactin, cortisol and insulin. 

As early as day 2 or 3 postpartum, moms experience swelling of their breasts as well as increased amounts of milk. In some cases, there is a lower milk volume. This is usually seen with women who had cesarean births (as opposed to vaginal). 

Late onset of milk production can occur in women who retained fragments of the placenta or had stressful vaginal deliveries. 

Phase 3: Maintain speed

Time for some cruise control. In phase III of Lactogenesis, the body is now under autocrine (rather than endocrine) control. There’s a maintenance of milk secretion and mature milk is established. This usually takes place at around day 10 postpartum and lasts until weaning begins. In order to maintain milk supply, the hormones prolactin and Oxytocin are essential. 

There’s some interesting facts about oxytocin, and it’s one of the six lesser-known benefits of breastfeeding. Every time you breastfeed, the stimulation triggers a release of oxytocin that tells your body to “let down” milk so your baby can drink. Oxytocin is also a wonderful promoter of overall mother-child bonding, which in turn fosters love, nurturing and a deep emotional bond between you and your little one. 

We also touched on this in our ‘explaining the let-down reflex’ post. During this reflex, specific hormones are released into your bloodstream; in particular, prolactin to stimulate milk production and oxytocin, which triggers the breast to let down the milk and makes the milk ducts widen so that it’s easier for the milk to flow. 

Phase 4: Pump the breaks 

We’ve reached the final phase of lactogenesis, in which breast milk secretion ceases. This usually happens about 40 days after you last breastfeed, give or take. The process of decreased milk production happens by apoptosis, which essentially works to maintain balance of the body. 

We know that  40 days is a long time. That's why weaning takes time, and you have to take it a bit slowly to avoid clogged ducts. 

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