Breastfeeding and Uneven Milk Supply

breastfeeding and uneven milk supply

Just like with many other components of the human body, it's not all perfectly symmetrical. In terms of breast tissue, breast milk production and the number of lobules containing the alveoli holding and making milk, symmetry, or lack thereof, applies here, too. Additionally, some women have more obvious and noticeable differences between breasts, and find it uncomfortable, physically or self consciously. Causes of uneven breast milk supply and lopsided breasts can be due to:

  • The physical design of each breast; uneven development of alveoli during puberty; normal to certain degree
    • Insufficient Glandular Tissue (IGT), a more severe lack of adequate tissue instead of just an imbalance
  • Side preferences
    • Baby preferring one side over the other for various reasons (see below)
    • Mom is more comfortable feeding baby on one side or the other
  • Pumping milk, with one breast responding better than the other
  • Breast surgery - whether removing tissue or changing the size, changing the internal anatomy may affect breast supply through physically removing or changing the tissue the breast produces milk with, or damaging the nerves that allow the response to stimuli. Work with an IBCLC to manage milk supply and form a care plan.
    • Mastectomy
    • Augmentation
    • Reduction

Since breast milk supply is also based on demand and the amount of milk output, a long-term pattern of feeding off of one breast more frequently can increase milk supply from the preferred breast.

The good news is, one breast can keep up with supply needs. A great example being women who have had cancerous breasts removed, mastectomy, have been able to still breastfeed exclusively on the other breast. The exception to this possibility is IGT, insufficient tissue on either side, which may impact this option. The bad news is that it can be quite uncomfortable having the weight of all the supply needs coming from one breast, and feeling lopsided in comparison to the other. This can be physically noticeable, too, which may be a discomfort. 

In many cases, measures to correct or improve the imbalance can be initiated, especially once the root cause is identified. An IBCLC , lactation consultant, can help identify the cause of discomfort and provide tools to help the mother improve breastmilk supply output.

Side Preferences

Baby has a Side Preference

In some cases, a baby may have a noticeable discomfort or displeasure on one breast versus the other, or simply having a preferred breast to breastfeed from. From controlling the letdown response, to just the ability to keep the breast tissue in the mouth to breastfeed, there are a variety of issues that lead to side preferences when breastfeeding. This can be caused by the following, but not limited to:

  • Torticollis, shortening of the neck muscles, tension, causing limited range of motion and misalignment
  • Ear infection
  • Maternal issues for regulating milk supply, having less milk on one side that further perpetuates the preference on the baby's end. i.e. mastitis, engorgement, clogged milk ducts, lower milk production due to IGT, uncomfortable with nursing positions switching from left side to right side/vice versa.
  • Tongue or lip ties, inadequate oral range of motion, causing tension
  • Engorgement in the mother, especially if on one side more than the other, making it difficult to remove milk. The problem is further perpetuated if not fed from engorged breast to relieve.

Mom Has a Side Preference

Most people are not ambidextrous, we are left- or right-handed. This can translate to having an arm we prefer to carry baby with, which way they lay when we change diapers, and which side we comfortably feed from. This is OK!  But because of this, it is important to be more conscientious when switching breasts to avoid one breast producing less milk than the other or causing the baby to feed with more difficulty on one side. 

  • Make sure baby faces you with the entire body, not just their head. This also helps with milk flow control for them!
  • Aim the nose at the nipple, not their mouth, to encourage a wide gape, deeper latch
  • Avoid pushing their head; instead, support the neck and base of the head.
  • Try different positions!
  • Work with an IBCLC
  • Pump on the side that needs to increase milk supply after feeding baby until even (may take a few days to a week)

Pumping to Correct Uneven Milk Supply

As previously mentioned, pumping after feeding from the "slacker boob" may help, as it increases stimuli and essentially sends a message to the brain to produce more milk. 

Pumping gives us a window of what our breasts provide individually, but it's not exact. Therefore, do not use pumping as an indicator of actual milk supply capabilities. 

If exclusively pumping and notice an uneven milk supply, examine your pumping techniques as well as the pumping schedule. The breast that does not output enough breast milk may need a power pumping routine, which may look like 10 minutes of pumping, resting for 5 minutes, and pumping again for 10 minutes. This can be done more than once a day.


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