Why does one breast produce more milk

…When baby prefers one side, or when supply or breast size is greater on one side

• Is this a problem?
• Why does it happen?
• Evening things up
• Persuading baby to nurse better on the less preferred side
• Will baby get enough milk?

Is this a problem?

Most women notice differences in milk supply, pumping output, milk flow and/or size between breasts. As with many other things (foot size, ring size, eyesight, etc.) asymmetry is normal in humans. In some women the difference between breasts is hardly noticeable; in others it is very noticeable. There is every variation in between. This is not usually a problem in terms of the breastfeeding relationship, so you certainly don’t need to do anything about it if the asymmetry does not bother you or baby; however some mothers prefer to even things out, particularly if there is a very noticable difference in breast size.

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Sometimes babies will refuse or fuss at a breast when the let-down is slower or too forceful, or the supply a bit lower. They in turn will prefer the side which lets down more/less quickly and in which the supply is more bountiful.

Why does it happen?

Possible reasons for variations in supply/milk flow between breasts:

• Normal anatomical differences. All women have one breast that has more working ducts and alveoli than the other (usually the left side, though either is normal). Some women also have differences between the two areola/nipples (inverted, flat, different shape/size) which make it easier for baby to latch on to one side than the other.
• Baby’s preference for one side. Most babies have a side preference to some extent. From the start, your baby may feel more comfortable being held on one side and therefore nurse it more efficiently and/or more frequently.
• Mother’s preference for one side. Mom (consciously or subconsciously) may offer one side more than the other because she feels more comfortable nursing on that side.
• Breast surgery or injury.If one breast was ever operated on or injured in any way, supply and/or milk flow can be affected.

If your newborn is refusing one side, have her doctor do a good physical exam to check for birth injuries. Some babies will have an injury that goes unnoticed at birth, but causes baby discomfort when in certain nursing positions.

If baby suddenly begins to refuse one side, it could be caused by an ear infection or other illness in baby (making nursing painful or uncomfortable on that side), an injury to baby (or something else, such as a sore immunization site) that makes nursing painful in that position, or a breast infection in that breast (which can make the milk taste salty). Many babies who refuse one side do so because mom has a much faster or slower letdown on one side (baby might prefer either the faster or slower flow). If all other possible causes are ruled out and baby continues to refuse one side, then consider seeing your doctor just to rule out any breast problems.

Evening things up

It is fine to just do nothing, but if the lopsidedness is bothering you, you can try to increase milk supply on the smaller side to increase the supply/breast size/milk flow on that side. Be careful, though, not to neglect the larger producing breast too much and allow too much backup of milk in that breast, because that may make you vulnerable to plugged ducts and mastitis.

Here are some things that can help to even things up (you don’t need to do them all; start off with the one thing that looks most workable for you):

• Start baby on the smaller side for each feeding for a few days (baby usually nurses more vigorously on the first breast offered).
• Nurse on the smaller side twice as often. For instance if you nurse on one side per feeding, you might nurse on the small side for two feedings, the larger side for one, then back to the smaller side for the next two feedings, etc.
• Pump the smaller side for 5-10 minutes after some feedings.
• Add an extra pumping session (for 10-20 minutes – smaller side only) in between feedings.

If the larger side becomes overfull, express just enough milk to relieve the pressure. Most mothers notice an “evening out” of some proportion within 3-5 days of doing these things. Most moms use these measures for a short time only, until they get the desired results, but others continue long-term.

There may always be a small degree of difference in breast size – at least to your own eyes. If there is an obvious difference in appearance through your clothing, you may want want to use nursing pads to give a more even appearance. Usually a difference in size is much more noticeable to you than to anyone else.

Persuading baby to nurse better on the less preferred side

• Try starting your baby on the preferred breast and then once let-down occurs, slide her over to the other side without changing the position of her body. For example, start her in the cradle position and then slide her over into the football position.
• Continue to try different nursing positions.
• Offer this breast to your baby when she is just waking up but not fully awake or already a little sleepy. She is more likely to instinctively nurse at this time.
• Nurse in a darkened and quiet room.
• Offer this side with motion; i.e. walk, sway, bounce, rock, etc. until your baby starts
  nursing well.
• If let-down on the less preferred side is too fast or slow, follow the suggestions in Let-down Reflex: Too slow? or Forceful Let-down Reflex
• If supply on the less preferred side is low, follow the suggestions above and in Increasing low milk supply.
• If baby seems to want a faster flow from the less preferred side, then try doing breast compressions to speed the flow.
• See the suggestions in Help — My Baby Won’t Nurse!
• Patience and persistence are key. Keep trying, and praise baby when she nurses well. Most of the time a baby will take the less-preferred breast with time. If baby is refusing or nursing rarely on one side, you may need to pump this side as often as the baby is nursing the other side in order to better maintain your milk supply.

Will baby get enough milk?

Yes – your baby can get all that she needs as long as she is allowed to nurse as often as she wishes – even if you nurse exclusively on only one side. If there is simply a difference in supply between breasts, baby will adjust her nursing to compensate. Overall milk production is generally not a concern unless other factors are involved.

If baby is completely refusing one side, you’ll want to pump that side as often as she nurses to maintain supply until you get her back nursing on that side.

If all else fails, one-sided nursing is very possible as long as your baby is allowed to
nurse without restriction. The side that you are not nursing on, once allowed to “dry up,” will be smaller than the other side. This will result in some degree of lopsidedness (though it may not be obvious), but this will remedy itself once weaning occurs.