Most women do notice a difference between their two breasts, when it comes to the flow of milk, the volume expressed and size between the two breasts; this is normal; no two sides of a person's body are the same. Most of the time, the difference in breast size is not obvious to others.
It is perfectly okay to continue to let your baby feed from only one side, while you pump the other, or even let it dry up; this is a personal decision.
Is Breast Preference Normal?
Breast preference is a common breastfeeding problem(1); newborns, especially, sometimes have periods of preferring one breast. Usually, a baby will start to pull away or fuss at the one breast.
If Baby is Refusing One Breast, will he be Getting in Enough Milk?
Unless you have low milk supply issues, If you breastfeed on demand, your baby will receive all they need from just one breast. Twins and even triplets only have two breasts to share, and many mothers have successfully breastfed multiples.
The more your baby drinks from one side, the more that breast will produce, so yes it is possible to breastfeed from one breast alone; most mothers would not want to do this, as it might cause them to look a little lopsided until they wean, that is. Read the suggestions below on how to avoid and remedy this.
How to Tell whether Your Baby's Getting Enough Breast Milk
So what Causes One Sided Nursing Preference?
Why does my one breast have a higher supply/faster flow?
Breast engorgement on one side may cause single-side-breastfeeding. The stiffness of the breast may cause latching difficulty.
Differences in the nipple (one is maybe easier to latch onto) A mole or even hair can bother a baby on one side. Different nipple variations. Anatomical differences between two breasts are common. Some mothers also have a more significant than usual difference in the amount of glandular tissue in each breast.
Flow differences between the two breasts; your baby might prefer the one breast with a more relaxed or faster flow of milk.
Forgetting to switch from one breast to the next will cause low milk supply in the breast that was neglected. Learn more about how breast milk production works.
If you have mastitis in one breast, your baby might not want to drink from it, due to the taste difference. Plugged ducts, stasis, and mastitis will increase the sodium levels in your milk and make the milk unpalatable. Breast massage is a great way to reduce the salt in your breast milk.
Breast milk may taste different (usually saltier) in one breast if it has a lower supply than the other. To remedy this, you can increase your milk supply on that side, by pumping.
One breast might have a darker color breast milk, this is usually due to a broken capillary and might cause a different taste; keep trying, after your breast has healed, your baby should start drinking from it again. Learn more about blood in breast milk here.
Maybe your baby won't latch on one side because he/she is more comfortable on the other side. Most babies show a side preference and will nurse more efficiently from that side. A mother may also consciously or unintentionally nurse from one side more often because she feels more comfy on that side.
Breast surgery on one side can cause a lower milk supply, which can be the cause of your baby refusing one breast.
The baby might have a sore inside his/her mouth. A blocked nostril or ear infection that causes pain during breastfeeding on only one side.
Sometimes birth trauma can cause a stiff neck on one side, making it more difficult to lay on one side. There may be other undetected birth injuries which may affect whether your baby prefers one breast. You could get a chiropractor to do a physical exam to rule out any injuries that your baby may have.
Low supply and refusal to drink have been found to occur when the ducts are filled with cancerous cells. One sided nursing can also be due to previous breast cancer treatment on one breast. Learn more about breastfeeding and cancer.
What Can I Do?
If there is a noticeable difference in breast size, some mothers may wish to even things out a little, here we will discuss how.
Remember, neglecting the breast that your baby loves should be avoided too, as this could make you more susceptible to plugged ducts and breast infections.
Pump the emptier breast for at least 10 minutes after every feeding, or until the breast seems empty. Use a quality breast pump, electric is best; this will keep your supply up. Adding a 10-minute pumping session on the emptier breast in-between feedings will also increase the milk supply on that side.
Try to breastfeed twice as much from the rejected breast. For example, if you usually breastfeed from one breast per feeding, breastfeed from the rejected breast for two consecutive feedings. If the larger breast becomes overfull, you can express enough milk to reduce any engorgement. After trying this, you should notice a more balanced production of breast milk within 4 days. If the problem is resolved, great, but know that some mothers have to proceed to use this method for as long as they continue to breastfeed.
Try offering the least desired breast first with every feeding. A baby will usually nurse more from the first breast offered. Alternatively, if you allow your baby to start on the preferred breast, you can switch sides when the let-down begins while attempting not to change the position of their body. An example of this would be to start out breastfeeding in the cradle hold and then slide your baby over to the football hold.
Try offering the least desired breast when your baby is half asleep so that he/she is tricked into nursing on the other side. ;-)
Massage your emptier breast; this will not only increase milk supply but helps to avoid clogged ducts. Breast massage before, during and after breastfeeding sessions are recommended to increase supply in the smaller breast.
If your baby seems to choke more on the one breast when feeding, it is probably a sign of a forceful letdown; you can first pump a bit of milk to decrease the flow, before offering the breast to your baby. A let-down that is too fast or too slow can be rectified.
Never force your baby to breastfeed from the undesired breast, you might cause a complete nursing strike.
If your one nipple is a little different and seems to be causing a problem, you can use a nipple shield. Also, here is a page about breastfeeding with flat or inverted nipples.
Sometimes offering the smaller breast while swaying, walking or bouncing may encourage nursing from that side.
Once your baby is satiated, you can use the less preferred breast to comfort feed. The sucking and stimulation will help increase your supply.
Nurse in a quiet, dim-lit room to limit distractions.
Breastfeeding your baby in a warm bath could relax him/her and encourage them to breastfeed from the other side.
If all else fails, pumping the rejected side will keep the milk flowing, once your baby accepts that side again, your milk supply will increase naturally. If you are not worried about being lopsided, you can allow the other breast to dry up. Most babies who are refusing one breast will usually take that breast over time, especially when they become more experienced at breastfeeding.
Try to visit your local la leche league, they can asses the situation and advise accordingly; their services are free.
If it's not bothering you, it's really okay to do nothing about the lopsidedness. Your breasts should even out again after weaning.