Pre-implantation genetic screening using a Trophectoderm (TE) Biopsy
With advances in assisted reproductive technologies, physicians are now able to offer couples genetic screening of embryos prior to placing them into the uterus during an in vitro fertilization (IVF) cycle. This method of embryo screening is now commonly referred to as pre-implantation genetic screening or pre-implantation genetic diagnosis.
- Pre-implantation genetic screening (PGS) refers to the general testing of the genetic chromosomes and is most commonly used to screen for Down’s syndrome (trisomy 21).
- Pre-implantation genetic diagnosis (PGD) refers to testing for a specific genetic disorder, such as cystic fibrosis.
There are various techniques that can be used for getting genetic material from an embryo, and more recently trophectoderm biopsy has been shown to be beneficial.
Once an embryo has reached the blastocyst stage (typically on Day 5) a trophectoderm biopsy can be performed. By the time an embryo reaches the blastocyst stage, cells of the embryo have differentiated into cells that are going to become the fetus and cells that are going
to become the placenta.
During a trophectoderm biopsy, cells from the placenta are removed and cells from the fetus are not disturbed. This is an important advantage of a trophectoderm biopsy. Another advantage of a trophectoderm biopsy, is that approximately five cells are removed for analysis rather than one cell, which is the case with other embryo biopsy methods. By increasing the number of cells for genetic analysis the accuracy also improves, making trophectoderm biopsy more reliable form of pre-implantation genetic screening.
Transfer of Embryos after Trophectoderm Biopsy
Once cells have been extracted from a blastocyst embryo for trophectoderm biopsy, the embryos are frozen and stored until the genetic results are available. Within a few days, your physicians will know the results of the trophectoderm biopsy and will review with you how many embryos have normal genetic chromosomes and how many were abnormal. Couples will then be able to choose which embryos, they would like to transfer into the uterus. This can usually occur with the next menstrual cycle.
Only a select number of IVF centers have the ability to perform a trophectoderm biopsy. Be sure to ask your doctor regarding if a trophectoderm biopsy is right for you when considering genetic screening of your embryos.
Another advantage of a trophectoderm biopsy, is that approximately five cells are removed for analysis rather than one cell, which is the case with other embryo biopsy methods. With increasing the number of cells for genetic analysis the accuracy also improves, making trophectoderm biopsy more reliable form of pre-implantation genetic screening.