Like weaning from the breast, weaning from pumping is best done slowly. This allows milk supply to decrease slowly, without fullness or discomfort.
There are a few ways you can approach weaning from the pump:
Drop one pumping session at a time.
Try dropping one pumping session every 3-7 days. For example, drop the first session on day 1 (while pumping regularly at other sessions), the second session on day 4, the third session on day 7, etc.
Let your comfort be your guide. Many women need to transition more slowly than simply dropping a pumping session all at once. You can do this by decreasing the amount of time (or volume) you pump each day until you are no longer pumping at that session; at that point you can start decreasing pumping duration for the second session.
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Gradually decrease pumping time for every pumping session at once.
Try decreasing all the pumping sessions you are dropping by two minutes every other day. For example, if you normally pump for 20 minutes at each nursing session, then on days 1&2 pump for 18 minutes, on days 3&4 pump for 16 minutes, etc. You may find that you can pick up the speed slightly, or you may need to go slower than this. Let your comfort be your guide.
Gradually increase the length of time between pumping sessions.
Instead of keeping pumping sessions at their regular times, gradually lengthen the amount of time between sessions. As usual, let your comfort be your guide. This will gradually decrease the number of pumping sessions. For example, if you normally pump every 3 hours, try pumping every 3.5 hours on days 1-3, every 4 hours on days 4-6, etc. Gradually decrease the duration of pumping sessions as you feel comfortable doing so.
Making It Work: Weaning from the Pump from New Beginnings, Vol. 20 No. 5, September-October 2003, pp. 183.