For many years, clinics have been performing “fresh IVF cycles,” where IVF is a fertility treatment in which a woman’s eggs are retrieved and fertilized using the partner’s (or a donor’s) sperm. Any resulting embryos are left to develop over two to five days and monitored for quality. One or two viable embryos are then transferred back into the uterus, 3 to 5 days later, in the hopes that the embryo will implant in the uterine lining. Good-quality embryos that remain can be vitrified (frozen) for transfers in the future.
Thanks to the advancements in reproductive genetics, some clinics are recommending something called a “freeze-all” cycle. This means that rather than transferring a fresh embryo after retrieval and fertilization, the embryos are immediately frozen so that they can have genetic testing done to help ensure the viability of the embryos, prior to transfer. This can help the outcome of the IVF cycle.
Advancements in Embryo Freezing
Embryo freezing technology has advanced greatly over the years. Embryos are now frozen via a process called vitrification. Vitrification is an ultra-rapid process that prohibits the formation of ice crystals. The process also uses cryoprotectants, substances that protect tissue from damage during freezing. Prior to the use of vitrification, a slow freeze process was used, which often compromised the quality of the egg or embryo. Today, vitrification has very little (if any) impact on the embryo.
What IVF Genetic Testing Is Available
There are two tests that can now be performed on a patient’s embryos, prior to selecting one for transfer – Pre-implantation Genetic Testing for Monogenic Diseases (PGT-M), formerly known as PGD, and Pre-implantation Genetic Testing for Aneuploidy (PGT-A), formerly known as PGS. PGT-M is available for patients who have been identified as carriers of the same condition as their partner, who have a diagnosis of a genetic condition, or who have a family history of a genetic condition that they were identified to have an increased risk of passing onto offspring. PGT-A is an optional test for all individuals undergoing IVF, who want the extra security of identifying the correct number of chromosomes in embryos, in hopes of improving IVF outcome. Patients can discuss both tests with their doctor to determine if testing is right for them. They may choose to have embryo testing to confirm that the embryo has a normal number of chromosomes, or see if their embryos contain a certain genetic mutation that can result in disease.
Genetic testing on embryos entails taking a small biopsy on day 5 or 6, at the blastocyst stage. The embryos are frozen after the biopsy and are later transferred once the health of the embryo has been confirmed. Confirming that the embryo being transferred does not have an extra or missing chromosome can decrease the chance of a miscarriage and increase the chance of implantation.
While genetic testing on embryos may not be covered by your insurance, it can still be worth looking into. Even in the absence of a family history, you can discuss the option of having a blood test (carrier screening) with your physician. This blood test can determine whether you are at an increased risk to have a child affected with a genetic condition, in which case PGT-M may be available. Knowing that you’re transferring an embryo that is more likely to be healthy can bring peace of mind to your IVF cycle. Should the embryo implant and a pregnancy be achieved, you can rest assured that the chances of having a healthy baby are in your favor!