Lopsided Breasts From Breastfeeding

Unevenness is common and normal, but there are ways to address it

Mother breastfeeding son while sitting by window at home
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Lopsided breasts while breastfeeding are common. You may experience varying degrees of unevenness in your breasts during the time you are breastfeeding. Depending on which breast you last nursed on and whether you breastfeed from one side or both sides at each feeding, your breasts will fill up with breast milk at different rates.

As long as your child is getting enough breast milk and growing at a steady rate, uneven breasts aren't anything to worry about. And some people naturally have uneven breasts regardless of breastfeeding. But, if you're uncomfortable or it bothers you, there are some things you can do to try to get your breasts back to a similar size.

Why Breasts Become Lopsided

If one breast gets more stimulation (from a baby nursing or from a breast pump), it will produce more milk and grow larger than the other one. Uneven breasts can happen when a baby prefers one breast over the other or if you start nursing on the same breast most of the time.

Unevenness is usually more noticeable during the first few weeks after the birth of your baby when your milk supply is still adjusting. However, even after the first few weeks, your breasts can still become lopsided, particularly if you tend to nurse your baby on one side more than the other.

How to Even Out Your Breasts

Start every feeding on the smaller breast until that side catches up in size. After a few days, the smaller breast should begin to make more breast milk, and you should notice your breasts becoming more balanced.

If your baby has a breast preference and refuses to nurse on one side, try to figure out why. It could be that the nipple on that side is flat or inverted, or that your baby has tight neck muscles (torticollis) that make it more difficult for them to turn their head in the direction of one breast.

After you breastfeed your baby, you can use a breast pump to stimulate your smaller breast further. Pumping can increase breast milk supply, which should help to increase the size of the breast.

Do not completely neglect the larger breast or it could end up becoming the smaller one. Keep the milk supply up in your larger breast by pumping the milk in that breast while you're spending more time breastfeeding on the other one.

You may also need to pump because your larger breast may become overfull with breast milk. You can pump or ​hand express a little of your breast milk from that breast to relieve the pain and pressure and avoid the complications of ​​breast engorgement. You can collect and store that breastmilk to use at a later time.

Once your breasts have evened out, go back to alternating the breast you start each feeding on to help keep them from becoming lopsided again.

Breastfeeding From Only One Side

If you breastfeed from only one breast at each feeding, your breasts will probably be uneven. The breast that you just breastfed on will be smaller, and the other side will be filling up with breast milk for the next feeding. Then, after the next feeding, it will be the opposite.

As long as you don't mind, it's not a problem at all. In fact, this fluctuation in breast size in relation to when you last breastfed on that side is completely normal, However, if you would rather your breasts stay more even from feeding to feeding, you can breastfeed from both breasts at each feeding to keep them more balanced.

When Are Uneven Breasts a Concern?

For most people who breastfeed, uneven breasts are not a medical concern. But, if one breast has been consistently smaller from the beginning and did not get any larger throughout your pregnancy or the early postpartum period, talk to your doctor.

Although it is rare, a small percentage of people have hypoplastic breasts, which is also called insufficient glandular tissue (IGT), a condition that causes insufficient or no milk production and could affect just one breast. If this is the case, you may not be able to even out your breasts, but you can still breastfeed. 

1 Source
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  1. Arbour MW, Kessler JL. Mammary hypoplasia: not every breast can produce sufficient milk. J Midwifery Womens Health. 2013;58(4):457-461. doi:10.1111/jmwh.12070

Additional Reading
  • American Academy of Pediatrics. New Mother’s Guide to Breastfeeding. Bantam Books.

  • Lawrence RA, Lawrence RM. Breastfeeding A Guide for the Medical Profession, Eighth Edition. Elsevier Health Sciences.

By Donna Murray, RN, BSN
Donna Murray, RN, BSN has a Bachelor of Science in Nursing from Rutgers University and is a current member of Sigma Theta Tau, the Honor Society of Nursing.