My nursing baby cries at the left breast and not at the right. Why?
There are several potential reasons why a baby might prefer one breast over the other. In some instances, it can relate to the size or shape of the breast itself, such as having an inverted nipple or one breast that's larger than the other. Both factors can make it more difficult for a baby to latch.
Differences in milk supply itself—either too much or too little—can also cause a nursing baby to prefer one breast over the other. Engorgement, which typically occurs in the newborn period (if at all), can easily make one breast much fuller and harder to latch on to than the other. If this is the case, it can help to express a bit of milk by hand or with a breast pump from the overly full breast so that it's not as full before nursing in order to make it easier for your baby to latch on. Differing amounts of milk production on one side compared to the other can also result in less milk and/or slower flow on one side, leaving a baby dissatisfied and fussing for more. If your left breast is the one that seems to make less milk than the right, it's worth being aware that consistently feeding on the "favored," more productive right side is likely to exaggerate the uneven milk supply even more.
Fortunately, having a baby who prefers one breast over the other doesn't tend to pose any serious concerns so long as they are getting enough to drink to gain weight well and be satisfied.