Choosing which embryos to transfer into your uterus for the best chance of a successful pregnancy doesn’t have to be a gamble.
Some women may choose to take control with preimplantation genetic screening (PGS), also known as preimplantation genetic testing for aneuploidy (PGT-A). But how does it work? How much does it cost? And what can it do for you? Here’s a guide to help you understand so you can make confident decisions about your treatment.
What is PGS?
PGS is a genetic screening test that determines whether an embryo has a normal number of chromosomes, which is an embryo quality essential for viability.
When a normal mature egg containing 23 chromosomes is fertilized with a normal sperm (containing another set of 23 chromosomes), the resulting embryo should have 46 chromosomes. However, many embryos start out with an incorrect number of chromosomes stemming from an abnormal egg, sperm, improper chromosome movement within the fertilized egg, or an abnormal cell division in the embryo. Embryos with 46 chromosomes in each cell are called euploid embryos. Embryos with an abnormal number of embryos are called aneuploid embryos.
Can the embryologist tell which embryo has a normal number of chromosomes using a microscope?
By day four or five after fertilization, embryos develop into blastocysts, a signal that it is the ideal time for them to be transferred into a woman’s uterus. But it is impossible to accurately distinguish which embryos are normal (euploid) or abnormal (aneuploid) just by looking at them under a microscope.
How is PGS done?
First, there's the PGS Biopsy, where a small number of cells are removed from each blastocyst in a manual procedure performed by a skilled embryologist.
Samples are then prepared and sent to a PGS laboratory. This step is done by courier in dry ice because the PGS laboratory is usually a separate entity from the IVF lab. Embryos are cryopreserved (i.e. frozen) and can be thawed and transferred later, after the PGS results are available.
The PGS lab will use one of several established methods to perform testing of the number of chromosomes in each embryo cell sample. Examples of these methods are next-generation sequencing (NGS), comparative genomic hybridization (CGH), and single nucleotide polymorphism (SNP). These methods are superior to earlier methods because all chromosomes can be assessed in parallel, which dramatically improves the false negative rate of aneuploidy.
Blastocysts with a normal number of chromosomes are selected for subsequent embryo transfer. One of the selected viable blastocysts is thawed and transferred in a “frozen ET” cycle.
What are the benefits of doing PGS?
How you might benefit from PGS depends on your specific clinical profile and personalized probability of IVF success.
If you have a high IVF success rate
If you have a high probability of IVF success and your fertility doctor expects you will have many oocytes and embryos, then limit your embryo transfers to euploid embryos (normal chromosomes) to minimize the number of embryo transfers needed to have a viable pregnancy. Also, should you want to expand your family later, you will know how many viable euploid embryos are cryopreserved and available to you.
If you have a low IVF success rate
If you have a low IVF success rate and your fertility doctor expects you will have very few oocytes and embryos, then you will mainly benefit from avoiding the transfer of aneuploid embryos (abnormal chromosomes) which can result in pregnancy loss. Some women may not have any embryos that are euploid. While that is devastating news, this knowledge can prevent further loss of time and money in embryo transfers that are futile. Instead, you can focus on other decisions: 1) Whether to do another IVF cycle, 2) Batch IVF cycles to submit more embryos for PGS testing and maximize the chance of having at least one or two euploid embryos or 3) To consider IVF with donor eggs.
What are the risks?
The risks of doing PGS mainly pertain to the immediate risk of embryo biopsy and the risk of having inconclusive results.
Embryo biopsy in the hands of highly skilled and experienced embryologists has very low risk of damage to the embryo. Any damage is not known to result in birth defects, but rather would result in the embryo not continuing to develop. Asking your fertility specialist about the number of PGS biopsies performed and the IVF center’s PGS results is one way to learn about the center’s experience.
There is also a risk of having inconclusive results if the biopsied sample does not provide sufficient materials for testing or if the PGS results show that an embryo has some cells with both normal and abnormal number of chromosomes. Even if PGS shows that an embryo is euploid, unexplained problems with uterine implantation or other types of genetic or developmental abnormalities can still cause a failure to implant or pregnancy loss.
How much does PGS cost?
Most IVF centers will break down the cost of IVF into several components.
The PGS biopsy fee is charged by the IVF center because it is a service provided by the embryology lab. This fee typically ranges from $1,000 to $3,000. Some IVF centers offer special programs that include the PGS biopsy fee.
The PGS lab charges a package fee for testing a certain number of embryos or a per-embryo fee for testing each embryo. Ask your IVF center which PGS lab(s) are utilized and how much they charge.
There can be a shipping fee because the embryo biopsy samples must be shipped in dry ice and via courier, which can cost between $100 to $500.
Other services that are inherent in the use of PGS include freezing and storing the embryos (cryopreservation and storage fees) and the cost of thawing and transferring the thawed embryos.
The best time to make the decision about whether to use PGS is when you decide to do IVF. While there are some estimates for the number of euploid embryos to expect depending on your age, many factors other than age can greatly impact and predict IVF success.
One major goal as an IVF physician is to identify proven health interventions that will optimize the vitality of eggs, sperm, and embryos, leading to enhanced fertility and family building options for our patients. PGS offers an efficient use of time and money to minimize the number of embryo transfers needed to have a baby and also offers insight to patients with very low probabilities of success. By enabling selection of viable embryos, PGS also empowers patients and providers to use one embryo per transfer to maximize the safety and health of the resulting pregnancy.
Since the first IVF baby in the U.S. was born more than 35 years ago, in vitro fertilization treatment has become more efficient, though seemingly more complex.
Revered gynecologist and IVF specialist Dr. Howard Jones established the first IVF clinic in the U.S. and helped achieve the nation’s first IVF pregnancy. The “test-tube” baby was born on Dec. 28, 19811. It took 41 tries before the baby was conceived.
Decades later, in a 2010 New York Times interview2 (five years before his death), the late Dr. Jones advocated that the cost of IVF could be reduced and the chances of success increased if fertility experts were able to distinguish which one embryo would grow into a healthy baby, rather than transferring multiple embryos into a woman’s uterus.
That’s where preimplantation genetic screening, or PGS, comes in. Dr. Jones' long-standing goal of “one embryo, one healthy baby” is now a reality.
Dr. Ronald F. Feinberg is one of the Founding Partners of Reproductive Associates of Delaware, where he serves as Medical Director of IVF Programs. He received an undergraduate degree in Biology at LaSalle College in Philadelphia, and received his MD and PhD in biochemistry concomitantly at the University of Pennsylvania. He completed his residency in Obstetrics and Gynecology at Yale-New Haven Hospital in New Haven, CT and a fellowship at the University of Pennsylvania, Medical Center in Philadelphia. He is board certified in Reproductive Endocrinology/Infertility and Obstetrics and Gynecology by the American Board of Obstetrics and Gynecology.
Dr. Feinberg has been active in major national nonprofit patient advocate groups, including RESOLVE, the American Fertility Association, the PCOS Association and PCOStrategies. He received a Family Building Award from the American Fertility Association in 2005. He published a book in 2004 for patients, called Healing Syndrome O: A Strategic Guide to Fertility, Polycystic Ovaries, and Insulin Imbalance. He is widely published in peer-reviewed journals with a major focus on embryo implantation.