Magnetic-activated Cell Sorting (MACS)

Through a biological programme known as apoptosis, the human body identifies and destroys cells it deems inferior. Sperm marked for destruction by this programme—‘apoptotic sperm’—are indicated by the presence of a lipid called phosphatidylserine and, if used in fertilisation, can  lead to problems such as embryonic arrest and early-stage miscarriage.

As a cell-sorting method, MACS allows apoptotic sperm to be identified and separated from the rest of the sperm population, with the aim of using only healthy, morphologically-sound sperm for fertilisation. To work properly, however, it does require a semen sample with a rather sizeable minimum sperm concentration of 10 million per millilitre of semen.