Having one breast that produces less milk than the other, often called a “slacker boob,” is common for many breastfeeding parents. This asymmetry is rarely a concern, as the higher-producing breast often compensates. Understanding this phenomenon is normal, and there are many targeted strategies to encourage the less productive side to increase its output.
Understanding Asymmetrical Supply
The difference in milk production between breasts is often due to natural anatomical variation, reflecting that the breasts are “sisters, not twins.” One breast may contain a naturally different amount of glandular tissue or milk ducts, which determines its maximum milk-making capacity. Research suggests that about 70% of individuals produce more milk on the right side, but the reason is not fully understood.
A prior injury or surgery, such as a biopsy, reduction, or augmentation, can affect the internal structure of the breast, potentially interfering with milk ducts or nerve pathways. This structural change may limit the tissue’s ability to respond to hormonal signals for milk production. More frequently, the imbalance develops because the infant consistently prefers one side, leading to reduced stimulation on the less-preferred breast. Since milk production operates on a supply-and-demand basis, lower demand signals the body to decrease production over time.
Immediate Nursing Strategies
To encourage the less productive breast, the most effective strategy is the “start on the slacker” rule. The baby is hungriest and employs the strongest suck at the beginning of a feeding session, which is the best time to stimulate the lower-producing side. Offering the slacker breast first maximizes the demand signal sent to that side’s milk-making cells.
Another technique is “switch nursing,” which involves moving the baby back and forth between breasts multiple times during a single feed. For example, begin on the slacker side, switch to the more productive side once the flow slows, and then switch back to the slacker side. This repeated stimulation can trigger multiple let-downs on the less productive side, maximizing milk removal.
Optimizing the baby’s latch and position on the slacker side is important, particularly if the baby’s preference is due to discomfort or an ineffective latch. Experimenting with different nursing positions, such as the football hold or side-lying, can help the baby achieve a deeper latch and more efficient milk removal. Ensuring the baby faces the breast with their entire body, not just their head, promotes a better latch and helps the baby empty the breast more completely.
Targeted Mechanical Stimulation
Interventions using a breast pump or hand expression are effective because they provide targeted stimulation outside of the baby’s feeding schedule. Pumping the slacker side after the baby has finished nursing is a powerful way to signal for increased production, as it ensures the breast is fully emptied. Even a short, 5 to 10-minute pumping session immediately following a feed can boost supply on that side.
Using a power pumping protocol can mimic the cluster feeding behavior of an infant, providing intense stimulation to the lower-producing breast. A common protocol involves pumping for 10 to 20 minutes, resting for 10 minutes, and repeating this cycle for about an hour, focusing specifically on the slacker side. Before and during pumping or hand expression, applying gentle heat and massage can encourage milk flow and a faster let-down.
It is essential to ensure the pump flange size is correct for the slacker side, as nipple sizes can differ between breasts. An improperly sized flange can lead to inefficient milk removal and nipple pain, which decreases supply. After a pumping session, incorporating hand expression helps to remove the final drops of milk. This sends the strongest signal to the body to produce more milk.
Knowing When to Consult a Professional
While asymmetrical supply is common, certain signs indicate that professional evaluation is necessary, such as from an International Board Certified Lactation Consultant (IBCLC) or a physician. Seek consultation if the difference in supply is sudden and dramatic, which could signal an acute issue like a blocked duct or infection. Pain, a persistent hard lump, or any signs of infection, such as fever or localized redness, should prompt an immediate medical evaluation.
If you have consistently applied nursing strategies and mechanical stimulation techniques for several weeks without seeing an improvement in the supply imbalance, professional guidance is recommended. An IBCLC can perform a feeding assessment, check the baby’s latch and oral anatomy, and help determine if an underlying issue, such as insufficient glandular tissue, is contributing to the asymmetry. They can also help create a personalized, effective feeding and pumping plan.