Preimplantation Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is a reproductive screening test that can be performed on embryos created via in vitro fertilization (IVF).

Preimplantation genetic testing (PGT) is a reproductive screening test that can be performed on embryos created via in vitro fertilization (IVF).

PGT requires the removal of one or more cells from an in vitro fertilization embryo to test for chromosomal normalcy.

PGT can ensure that the embryo selected for transfer to the uterus has the correct number of chromosomes to reduce the chances of: 

  • Failed IVF cycle
  • Miscarriage
  • Birth of a baby with a chromosomal abnormality

What are chromosomes?

Chromosomes are threadlike structures found in most living cells’ nucleus that carries genetic information in the form of genes. Chromosomes contain all 20,000 of our genes that produce the signals for the development and future maintenance of the human body.

Usually, each of our cells needs 46 chromosomes, 23 that initially come from an egg and 23 from a sperm.

Maternal Age and Chromosomal Abnormalities

As a woman ages, she is more at risk of having abnormal chromosomes in an embryo. At 25, 75% of a woman’s eggs are chromosomally normal. By age 35, about 50% of eggs are chromosomally normal; at age 40, only about 10-15% are chromosomally normal.

PGT: What are chromosomes

Reasons to consider Preimplantation Genetic Testing (PGT)

For individuals who experience infertility or recurrent pregnancy losses, chromosomal abnormalities in an embryo may be a contributing factor. Many embryos are unable to successfully implant after IVF due to their abnormalities or specific genetic conditions that may have. Preimplantation genetic testing, which involves advanced embryo biopsy, addresses these conditions. It is one of the most significant breakthroughs in reproductive medicine.

Reasons fertility patients consider PGT:

  • A patient is over 35
  • Several miscarriages have occurred
  • A chromosome abnormality was present in a prior pregnancy
  • There have been several failed IVF cycles
  • There is a desire to balance the genders in a family

Hereditary Genetic Disorders

Some diseases, such as cystic fibrosis and muscular dystrophy, are caused by one gene mutation inherited from parents. If both parents, egg donors, or sperm donors are identified as carriers for a specific genetic disorder, there is a 25% chance that the offspring will be affected. This is called recessive inheritance.

Dominant inheritance is when one parent has a genetic disease. Their chance of having offspring with the same condition is 50%.

  •  An autosomal dominant genetic disease such as Marfan syndrome is present
  • There is a history of Huntington’s disease
  • A recessive genetic disease such as cystic fibrosis is present
  • X-linked genetic diseases like hemophilia, Duchenne Muscular Dystrophy, cystic fibrosis, and hereditary cancers

PGT provides control.

Genetic testing allows couples to identify the healthiest pre-embryos for implantation.

Genetic screening benefits women who conceive after age 35 because developing embryos are more likely to suffer chromosomal conditions.

Also, women who have experienced miscarriages or given birth to children born with chromosomal conditions are at higher risk in future deliveries.

There are many additional reasons to pursue genetic testing, such as gender selection for family balancing, identifying an embryo that is a genetic match for an existing child who may need medical treatment such as a bone marrow transplant, or personal reasons. Ultimately the desire to ensure a healthy baby is born is at the forefront of genetic testing.

PGT-A and PGT-M

There are two different types of genetic tests used for embryo evaluation:  

  • PGT-A is used to test for abnormal chromosomes and select the best embryos before implantation to increase the IVF success rate.
  • PGT-M determines whether you and your partner are at risk for having a baby with a genetic disease and selecting the embryos that do not carry the disease-carrying gene(s).

Both PGT-A and PGT-M can be done on the same embryo biopsy.

How is PGT testing performed?

With advancements in biopsy technology, cells from an embryo can be biopsied safely and screened with molecular techniques to determine which, if any, embryos are affected by chromosomal abnormalities.

PGT starts with the same initial process as in vitro fertilization. Eggs must be retrieved and fertilized outside the uterus in a laboratory.

Over the next five to six days, the embryo develops into a blastocyst. Once this occurs, PGT can be utilized and will include the following steps:

  • First, several cells are taken from the embryo, a process called embryo biopsy. The embryo is then frozen (vitrification) while testing on the cells is completed.
  • The biopsied cells are assessed in the laboratory to determine if an inherited or problematic gene has been passed on to the embryo or if other concerning issues exist.
  • Once PGT results come back and healthy embryos are selected, embryo transfer can proceed.
  • Embryos not used in the initial transfer will remain frozen to be utilized later.
PGT: Human Embryonic Development

By selecting and using the highest quality chromosomally normal embryos during IVF, the likelihood of implantation is maximized, and the chances of delivering a healthy baby are increased.

Family Balancing

Family balancing is used for gender selection to achieve a more balanced representation of both genders in a family. Many couples want control over the gender of their future child. Family balancing allows couples to ensure the desired gender through IVF and PGT. These procedures provide a scientific means to select the gender of the embryo that will be transferred into the uterus.

It is the sperm that determines the sex of a baby. If a sperm carries the X chromosome, the child will be female. If it has the Y chromosome, the child will be male. The World Health Organization (WHO) estimates the natural sex ratio to be 105 males to every 100 female births. That’s almost a 50/50 chance for one or the other gender. Those are tough odds if you have reasons to want a specific gender.

Factors influencing a baby’s gender include the father’s genetics. Some men inherit a propensity to have more sons or daughters. They may produce more sperm that carry X or Y chromosomes, resulting in more children of a specific gender.

Why family balancing matters to many patients

For some intended parents, having both genders in the family is very important. For others, one gender may be desired for all offspring due to an inherited genetic disorder of concern for a specific gender.

Preimplantation genetic testing gives them that control.

Our experienced team at LFI uses only the most modern medical technology to provide PGT for our patients.