A method for operating a breastpump unit for expression of human breastmilk and various breast shields for use in this method allow a maximum pumping performance and a minimum pumping duration per pumping session. The breast shield has an inner chamber for receiving a nipple of the breast and also at least one outer chamber which at least partially surrounds the nipple. The inner chamber is subjected to a constant pressure and the at least one outer chamber is subjected to a pulsating pressure.