Embryology Basics

The application of PGT analysis for embryos generated by in vitro fertilization (IVF) procedures is an extremely beneficial merging of two modern technologies designed to offer couples in need of reproductive assistance the best chance to achieve a healthy pregnancy. The wealth of genetic knowledge now available to aid medical practices makes this merger of IVF and PGT a tremendous advance. The mission of Fairfax Diagnostics is to use the very best PGT laboratory practices to interface with and support those efforts by reproductive medicine practitioners to serve their patients with the best possible care.

PGT Coupled with IVF

Merging Genetics & Medicine

Embryos created using standard IVF procedures are grown in the embryology laboratory for 5 to 6 days until they form an early embryo called a blastocyst. The embryo is subsequently biopsied to remove a few cells from the outer layer, also called a trophectoderm (TE), which is destined to form the placenta. The removed cells are subsequently used for PGT after the DNA (genetic material) is isolated and prepared for molecular analysis using the PGT test appropriate for the couple’s medical situation.


The removal of a few cells from the embryo at the appropriate time is called a biopsy. In preparation for the biopsy, oocytes (eggs) are fertilized with sperm using intracytoplasmic sperm injection (ICSI) on Day 0. This is important to avoid test errors due to sperm contamination. On Day 3, progressing embryos may undergo assisted hatching. This involves making a small opening in the outer layer of the embryo, which increases the likelihood of the embryo reaching the hatching blastocyst stage, so that a biopsy can be performed.


The biopsy will be done for all embryos that become a hatching blastocyst on Day 5 or Day 6 of embryo development. At this advanced stage of development, the outer layer, or TE of the embryo begins to break out of the protective shell of the embryo. The first few cells to emerge are removed and used as the starting point for all PGT assays. Because of the location of the biopsied cells, this procedure is called a TE biopsy or a blastocyst biopsy. The cells of the inner cell mass that form the eventual fetus are not disturbed during this process.


A key consideration for the merging of IVF and human genetics is the fact that the quality and accuracy of PGT results are dependent on the skill of the embryologist when performing the biopsy to yield high quality, intact cells. In other words, a high-quality biopsy will result in highly accurate and reproducible PGT results making the process a state-of-the-art medical accomplishment.


The biopsy, comprised of an average five cells, is quickly frozen and sent to Fairfax Diagnostics for DNA isolation and genetic analysis using PGT. This is the starting point for all 3 PGT tests; PGT-A, PGT-SR, and PGT-M.