In vitro fertilization (IVF) helps thousands of people become parents each year. IVF involves several different types of tests, screenings, and procedures in order to increase the likelihood of success. One such screening is PGS (preimplantation genetic screening) and PGD (preimplantation genetic diagnosis). This article provides an overview of IVF with PGS/PGD success rates.
Intro to PGS/PGD
What is PGS? Fertility clinics test for general chromosomal abnormalities using a process called preimplantation genetic screening. The simplest way to describe PGS is that it’s a general screening that looks for abnormal chromosome counts. Using PGS, embryologists can determine if the number of chromosomes in the embryo meets standards for normalcy and may increase IVF success rates.
PGD (preimplantation genetic diagnosis) is another form of testing, and it is more specific than PGS. PGD tests for specific conditions.
IVF with PGS Success Rates
Many fertility clinics and specialists suggest PGS/PGD to increase the success of IVF. As stated earlier, PGS identifies chromosomal abnormalities. Abnormalities lead to failed natural and assisted pregnancies, and that is the primary reason PGS increases IVF success.
Chromosomal abnormalities occur more often than people think. As women age, the likelihood of an irregular chromosome count only increases. At 28 years old, approximately 30% of her remaining eggs have chromosomal abnormalities. By age 40, almost 60% of her remaining eggs are abnormal, and by age 44, that percentage climbs to almost 90%.
Determining IVF with PGS success rates is possible, but contextually it’s important to realize that without PGS, embryos that have chromosomal abnormalities can be transferred fresh, or frozen for later transfer. Embryos with abnormalities often do not make it all the way to blastocyst phase, and if they do, can sometimes fail to implant. So in some ways, it is futile to compare IVF with PGS success rates to IVF without PGS, because chromosomally abnormal embryos do not have the same chances of success.
Does PGS Increase Success of IVF?
Logic suggests that by implanting embryos that are known to be normal, the likelihood of miscarriage or failed implantation goes down. Therefore, the IVF with PGS success rates should be higher than without it.
One clinic determined IVF with PGS success rates to have a 10% higher pregnancy rate. Live birth rate differences are inconsistent and therefore inconclusive. However, almost all studies and clinic data show that IVF with PGS success rates indicates higher pregnancy rates.
IVF with PGS/PGD results in a lower number of miscarriages than without it (from 9-10% lower with PGS to 38% lower with PGD). That’s a major benefit and source of assurance to women who have suffered many miscarriages prior to IVF with PGS. Miscarriage can be tragic, but even more so after going through the time, money, and discomfort of in vitro fertilization treatment. Because of this, women fertility clinics can reduce the likelihood of miscarriage through PGS/PGD, that is great news.
However, live birth rates are not necessarily higher with PGS. When looking at IVF with PGS success rates, it’s important to consider all of the success metrics, not just miscarriage rates. It’s unclear why there is an inconsistency with live birth rates, while miscarriage rates are lower.
The other thing to consider is that not all clinics report the same results. Some clinics have extremely high IVF with PGS success rates. Those clinics may specialize in IVF and PGS/PGD, and it is worth looking into how a clinic performs the screening. The screening method and clinic’s reputation for careful handling of embryos factors into the success rates.
Some clinics in US report success rates upwards of 75% pregnancy and live births, even for women well into their 40s. The reason for the success, according to the clinic, is the perfection of the process. It’s worth noting that the reason for testing is to avoid the transfer of embryos with irregular chromosome counts. By being careful and selective in choosing with embryos to transfer, a clinic can dramatically increase the likelihood of success.
Other Ways to Evaluate PGS Success
Success rates present just one way of looking at PGS success. Another way is by evaluating birth defects and genetic disorders. For example, PGS results in lower cases of Down’s Syndrome than without it. For women and couples with a higher risk of passing on genetic abnormalities, this information can be very useful and reassuring.
Risk Factors that Impact IVF with PGS Success Rates
Because embryos are so fragile, the process used for PGS matters a great deal. Damaged embryos may not implant, or could ultimately result in irreparable harm leading to miscarriage and IVF failure.
Several situations pose a certain risk to PGS:
- Embryo damage. If the biopsy is performed too early, or incorrectly, the embryo could suffer trauma that wouldn’t necessarily be easily identified.
- Errors in screening. Embryologists must know exactly what they are doing when it comes to PGS. Any errors in biopsy or handling could result in a failed transfer or implantation.
- Mosaic embryos. An embryo is said to be mosaic if there are 2 (or more) different chromosomal patterns in the cells.
Who Benefits from PGS/PGD to Increase IVF Success?
PGS/PGD can provide an additional layer of assurance that IVF has higher success rates in older women who generally have a greater chance of failed treatment. Eggs from older women (age 35 and older) are more likely to have irregular chromosome counts. Abnormal chromosome counts can lead to failed implantation, miscarriage, birth defects, or other genetic conditions. Many couples opt for PGS to provide a higher chance of a successful pregnancy and live birth.
Women who have had a lot of experiences with miscarriages benefit from PGS/PGD, as well, for the reasons mentioned above. Chromosomal abnormalities can cause miscarriage, and when there is no other obvious cause for repeat miscarriages, PGS can provide some much-needed answers and improve IVF success rates.
Couples, where one or both partners is a carrier of chromosomal translocation, should also consider PGS. Chromosomal translocation occurs when chromosomes are not arranged in a typical way.
Younger women and couples with no likelihood of carrying genetic abnormalities typically do not choose PGS/PGD. There is an additional cost with the screening as well as risk to the embryos, and therefore it is not something all IVF patients choose. Women under the age of 34 are less likely to have a high percentage of eggs and embryos with abnormal chromosome counts.
Women aged 40 and over should always opt for PGS/PGD if it is an option at their clinic because the risks are so high. Some patients may find that after PGS, no embryos can be transferred. While this news can be disheartening, it is easier to handle than a miscarriage due to a chromosomal abnormality, or a failed implantation. Both situations can be emotionally difficult to endure. PGS/PGD helps reassure patients that they have the absolute highest likelihood of a successful pregnancy.
How PGS/PGD Increase IVF Success Rates
As part of the normal IVF treatment, women take medications to stimulate their ovaries and help the eggs to mature. Doctors also prescribe medication to women to suppression ovulation. This allows doctors to time IVF treatment precisely, and to schedule an appointment to retrieve eggs, rather than letting the body ovulate and release just one egg (which is what normally happens).
Once the follicles in the ovaries are mature and the eggs are ready to be harvested, fertility doctors retrieve eggs carefully. During this process, as many eggs as possible will be collected.
Continuing with the normal IVF process, an embryologist fertilizes the egg with sperm collected from the woman’s partner or with donor sperm. If all goes well, all of the eggs will be fertilized and develop into embryos (2-3 days) and then blastocysts (5-6 days).
Once the blastocysts are formed, embryologists remove cells from each blastocyst and send them to be tested, or perform the tests in-house. Sometimes, an embryologist will remove cells prior to blastocyst phase. However, many experts believe that waiting until the embryos reach blastocysts is the safest strategy. While the testing occurs, the clinic freezes the blastocysts.
The PGS/PGD results determine whether or not an embryo has a normal number of chromosomes. If it does, the embryo can be used in the embryo transfer process and may increase IVF success. However, if it does not, patients and their physicians will need to determine whether or not to keep the embryo or discard it. Typically, only genetically normal embryos will be kept for transfer. The normal embryos that are not transferred can continue to be kept frozen for later cycles of IVF, or for embryo donation.