The procedure of removing one cell to test for either PGD or PGS is called Day 3 Embryo Biopsy.
On day 3 of embryo development, most normally growing embryos contain between 6 and 10 cells. Each embryo to be biopsied has a small opening made in the zona pellucida using a laser (this is the same technique that is used for embryo hatching). After the hole is made, one cell is removed using a very small pipet and this cell is sent to the testing laboratory.
The well being of a child born after embryo biopsy is not affected by the procedure. The remaining embryo is placed back into culture to continue development until the test results are received. In most cases the test results are received on the morning of day 5 and the healthy embryos are transferred on this day.