Breast preference

Why does my baby like one breast more than the other?

There are many reasons why a baby may prefer one breast over the other. They may dislike a breast that has a low or a large milk supply, a plugged duct, or an infection. They may be reluctant to breastfeed if they feel the mother tense up from pain or if the nipple is abnormal. In some cases, there is no clear cause; babies just prefer one side. Mothers can try to prevent the baby from developing a preference by changing the starting breast at each feed. If a baby feeds more on a preferred breast, the other one will produce less milk, making it even less appealing to the baby. To end a breast preference, mothers can start the baby on the less preferred side. Mothers can try to increase the milk supply on that side by expressing after feeds or breastfeeding the baby to sleep on that side. It is not uncommon for a baby to gradually reject one breast. While not ideal, this is not a reason for alarm as long as the baby is getting enough milk.

A) Causes of breast preferences

Some babies may be prefer one breast over another or may even reject one completely, while continuing to breastfeed well on the other one. 

1) Differences in milk supply between breasts

Most mothers have slight differences in breast size and in milk production between the breasts. Some babies like the side with more milk but if the mother has a large milk supply, the baby may find that breastfeeding on the less active breast is easier.

Some mothers are born with a problem that leads to a low milk supply on one side. In others, a low milk supply may develop after starting breastfeeding.

Sometimes the mother is more comfortable breastfeeding on one side. She may be trying to avoid painful breastfeeding or may be strongly right- or left-handed. This will increase the milk supply on one side and decrease it on the other and babies may come to reject the weaker side.

2) Differences in nipples

Some babies try to avoid a breast with an abnormal nipple or nipple root.

3) Changes in the breast

Some babies cannot or will not breastfeed on a breast with:

This can be due to changes in the nipple root or in the amount of milk the breast makes. If you notice any changes in your breast, please see your health-care providers.

4) Nipple pain on one side

Mothers who are in pain tend to be tense while breastfeeding and babies can sense this and be reluctant to breastfeed. 

5) No known cause

Finally, some babies just slowly come to prefer one breast without a specific reason.

B) The breast preference cycle

Breast preference can become more marked as it can create a cycle of decreasing milk supply on one side and increasing unwillingness to breastfeed on that side.

Every time a baby feeds poorly or not at all on one side, less milk is removed from the breast. This reduces the milk supply on that side. As there is less and less milk in the breast, the baby becomes increasingly unhappy on that side.

C) Preventing breast preferences

To prevent your baby from developing a strong preference for one breast, treat both breasts equally if possible. With each feed, change the side you start with. When expressing, do so effectively so that both sides are expressed equally well.

If you notice that you have a significantly larger milk supply on one side, start the baby on the weaker side.

D) Managing breast preference

1) Ensure the baby is fed

If a baby has a breast preference or if one breast produces significantly less milk than the other, mothers need to ensure the baby is getting enough milk and growing well. Some babies in this situation do not get enough milk and need to be supplemented with appropriate milk. It may be possible to increase the milk supply.

2) To end a breast preference

  • If possible, remove any breastfeeding barriers on the less preferred side.
  • At every feed, start the baby on the less preferred side.
  • Increase the milk supply on the weak side by:
  • If the baby needs supplements, consider using a tube-at-the-breast system on the weaker side to keep the baby breastfeeding and stimulate milk production. 
  • Consider using the tools that are used for a nursing strike or breast reluctance.
  • nipple shield might be effective.

If you are in pain when breastfeeding, try to fix the problems and control the pain as best you can so that you can relax during feeds.

E) Long-term outlook

Babies with a breast preference may resume normal breastfeeding patterns, others persist with a definite preference, and others gradually reject one breast completely.

If the breast has changed so that the baby can no longer latch or the milk supply is permanently reduced, it may not be possible to resume breastfeeding normally on that side.

If the baby will breastfeed at all, mothers should offer the weaker one first and consider breastfeeding the baby to sleep on that side to maintain milk production and minimize the chance of breast rejection. They can consider using a tube-at-the-breast system to encourage the baby to breastfeed.

Complete breast rejection can happen even if the mother tries to prevent it. This is not a cause for alarm as long as the baby is getting enough milk. A surprising number of mothers can provide enough milk by breastfeeding with one breast but others will need to supplement their babies with extra milk. Mothers can consider expressing on the affected side if the baby needs milk supplements or to help the baby resume breastfeeding on that side.

If a baby is only breastfeeding on one side and does not need supplements, that breast may have a large milk supply and may be at risk of associated problems. One study of women from fishing villages in Hong Kong who traditionally only breastfed on the right breast showed higher levels of breast cancer in the left breast after menopause (Ing 1997).


Ing R, Petrakis NL, Ho JH. Unilateral breast-feeding and breast cancer. Lancet. 1977 Jul 16;2(8029):124-7