Study procedures - Phase 1 The participant will be invited for a pumping session (3 times 2 minutes of expression) at Medela Headquarters. The CE-marked Freestyle breast pump and its pumpset will be used in the both phases of the study.The participants will be asked to pump 3 times with each of the 3 breast shields in a randomized order. Each pump session (defined as pump start till pump stop) will be short (2 minutes of pumping after milk ejection has occurred), and all three short pumping session will be done on the left side only. All pump session will start with the stimulation mode and change to expression mode as soon as milk flows.