It's not uncommon for some mamas to see a decrease in milk supply when they go back to work since not all of our bodies respond perfectly to the pump. (mamasaywhat.com)
Some women do notice a temporary drop in milk supply in the days just prior to a period and for a few days into one. (motherandchildhealth.com)
Some mothers see an increase in their milk supply while using this method, while most see no difference, and a few will see a decrease. (verywellfamily.com)