Why is one breast larger than the other?

I got a call the other day from a mama that was asking why one breast was bigger than the other and could she do anything to change it.

Many women notice that one breast makes more milk—or that the baby prefers one side over the other. Many breastfeeding mothers have one breast that makes more than the other. This is completely normal, but it can sometimes leave you wondering why it happens and what to do about it.

Many women have one breast that is slightly larger than the other. This may affect how much milk the breast may make. One may naturally have more milk-making (glandular) tissue, a different duct layout, or a stronger letdown reflex. There are some women that have a huge difference in milk capacity from one breast to the other. Some mamas can make up to 7-8 ounces in one breast and only a 1/2 ounce in the other. This can be normal for some women and because it is tied to the anatomy there isn't any amount of pumping that will change it.

Babies sometimes have a favorite side from day one. Maybe one nipple is easier to latch onto or your baby’s neck muscles are tighter on one side (often from birth position or tension), or the mama prefers holding the baby on one side over the other. Stimulation in the early days makes a difference to the milk supply. When a baby nurses more often on one breast, that side responds by making more milk—while the other gradually slows down. Good stimulation to both breasts is important to produce a full milk supply. And even then some breasts may not have much glandular tissue and hence not make as much milk. Some of us can store lots of milk in our breasts and some of us not so much. We can still breastfeed and most of the time make enough for our babies.

Uneven stimulation in the early days when woman are laying down the foundation for milk supply may affect how much each breast makes. Good stimulation to both breasts is important to produce a full milk supply. And even then some breasts may not have much glandular tissue and hence not make as much milk. One mama may need to breastfeed more frequently due to the difference in storage capacity. Some breasts are able to make a large volume and hold a large volume without getting too engorged. Remember, milk supply works on supply and demand. The more milk that’s removed, the more milk your body makes. So if you mostly feed or pump from one breast, the other won’t get the same signal to keep up. If your baby is having trouble latching to both sides in the first week, then consider pumping the side baby is not latching to as much to provide stimulation evenly to both breasts.

Past surgery or injury can affect ducts or nerves and reduce milk production on one side. Any damage to the glandular tissue and ducts will affect the milk supply. If a duct is cut then the milk can’t get out and will be trapped in the breast until it dries up. Nipple piercing can also affect the way milk is removed from the breast. If there is scar tissue blocking the ducts the milk removal will be affected. Breast reduction removes the glandular tissue and will severly affect the amputn of milk the breast is able to make. Breast augmentation may or may not affect milk production: it is dependent on the of type of surgery and where the incisions were made, as well as the shape and size of the breast before the augmentation.

Can I Breastfeed From Just One Breast?

Yes—you absolutely can. Many mothers nurse successfully from one breast only. That side will increase its production to meet your baby’s needs. The amount of glandular tissue will have an effect on the amount of milk one breast can make.

If you’re feeding primarily from one side:

• Keep an eye on the other breast for fullness or plugged ducts. Pump if your breast is full and uncomfortable. If you know surgery may be causing the blockage, then you can use raw cabbage leaves applied directly to the breast over the hard area to help that milk dry up.

• You can hand express or pump from the lower-producing side to attempt to increase supply. But remember if it is due to anatomy or trauma from surgery it may not make a difference.

• Offer both sides early on to establish a good milk supply in both breasts. If a baby will not latch to one breast, then be sure to pump in the early days to stimulate milk production. A deep, comfortable latch in the first 3-5 days is important to establish your supply. If your baby is not latching every 2-3 hours in the first 24-48 hrs and staying awake to feed, then get a pump and start pumping to provide good stimulation to the breast while you are waiting for professional help.

When to Reach Out

If your baby seems frustrated at the breast, isn’t gaining as expected, or if you’re dealing with discomfort or uneven fullness, we can help. Our International Board Certified Lactation Consultants (IBCLCs) specialize in assessing latch, milk transfer, and breast health.

Together, we will create a personalized plan to keep feeding comfortable and productive for both you and your baby.

If you’d like to talk through your feeding experience or have your milk supply evaluated, schedule a visit at Gulf Coast Lactation. We are here with expert, compassionate support every step of the way.