It is not unusual for mamas to produce more milk from one breast than the other.  The less productive breast is commonly (and lovingly!) referred to as a “slacker boob.”

A Deeper Look:

The thing about pumping is that you can always see exactly what is going on with your breasts.  You can see how fast the milk flows, how far your nipples stretch, the color of your milk, and whether one breast produces less milk than the other.  This last one—having a less productive breast—is not unusual, and the less productive breast is commonly referred to as a “slacker boob.”  In fact, in one study—titled Dynamics of Milk Removal During Simultaneous Breast Expression in Women—the researchers noted, “In 46% of mothers, one breast produced at least 25% less milk than the higher-producing breast.”

Why Does This Happen?

There are many reasons why one breast may produce less milk than the other, and you may never know the reason behind your particular situation.  Just remember, it is something many mamas experience!  Sometimes the reason may be based in anatomy.  Perhaps there is a disparity in the breast tissue development and you have more working milk ducts on one breast than the other.  Other times it may be situational: at one time, you more frequently removed milk from the breast that is now the more productive side (such as if you nursed your baby for a time and you or the baby more often offered or preferred one side).  Another possibility could be that you pay more attention to the more productive side while pumping via massage and breast compressions.  

Sometimes milk output is the only discernible difference between your breasts, other times there is a difference in appearance.  If this is the case for you, don’t forget that having uneven breasts are totally normal—even for women who have not lactated. 

Although a disparity in milk output between breasts is not cause for concern and it’s pretty common for most mamas to consistently have one breast that outperforms the other, if it bothers you, there are some things you can try to fix it.

Tips For Fixing a Slacker Boob

After you have finished your normal pump session, continue pumping for a few more minutes but only on the side producing less milk.  You could try pumping 5-10 minutes more and then stop or if you achieve another let-down before 5-10 minutes has passed, you can stop there.

Utilize breast compressions more often on the slacker boob side.  This does not mean ignoring your other breast; rather, make sure you are still utilizing breast compressions as much as you always were on both sides, but add more to the less productive side.

Another option is to add an additional pump session (try 5-10 minutes) or power pump but only on the the less productive side.  Most pumps allow for single-sided pump sessions by closing one of the valves.

You may not see any results from your efforts to fix the milk output of your less productive breast for a few days to weeks of consistently utilizing one of the tips to increase supply.  Remember, milk works on supply and demand!  And don’t forget that a health care professional can be a great resource here!

Other Things to Consider 

Before you go through the work of trying to increase supply on just one side, there are a few things to check or try that may help the milk disparity issue.  The first thing I would consider is whether your nipples require different sized flanges because that can result in a decreased output. So it’s worth checking whether you are using the correct-sized flange on your less productive breast.  Next, make sure your pump parts aren’t worn and in need of replacement.  Worn out pump parts can contribute greatly to a decrease in milk output.  You might also consider paying attention to whether you devote more time to massaging or hand expressing on your more productive breast.  Finally, a recent infection or injury to your breast could result in a sudden decrease in milk output on one side, here and here are two posts that discuss pain and pumping. If this last one sounds like you, make sure you speak to your health care professional. 

The EP&Me Take:

I had a slacker boob! My right breast always yielded less milk than my left.  For most of my pump sessions, the difference in output was between half an ounce and an ounce (more often an ounce).  However, if it was my morning pump, the difference at times could be two ounces!

In the early days, immediately postpartum, I always tried nursing my little one on the left breast first, and I wonder if that had any impact on why the supply for my left side was stronger.  Sometimes, I would try nursing on the right breast, but more often than not, my Little One had gotten really upset and we had moved on to the pumped milk in a bottle instead.  I’ll never know for sure, but I suspect my favoritism  of offering my left breast in those early days contributed to the increase in milk supply on that side!

I am also a mama that needed different sized flanges for each breast.  I didn’t have a great size discrepancy, but one side needed a 15mm flange and the other a 17mm flange for maximum comfort and output.  So it’s absolutely worth checking to make sure you are using the right sized flanges for both because the need for different sizes does happen!

Keep in mind that every bit of this motherhood journey is unique for each of us.  And breast size and milk output between breasts is no exception.  Having a less productive breast is normal and as long as you are okay with it, it’s nothing you need to take action on.  Happy pumping mamas!