If you are over 38 and considering IVF treatment, understanding egg quality, chromosomal health, and PGT-A (Preimplantation Genetic Testing for Aneuploidy) is essential.
In this webinar, Dr Silvia Cortell, Fertility Specialist at UR La Vega, Murcia (Spain), explains how fertility changes with age, why miscarriage risk increases after the late 30s, and how PGT-A can help identify embryos with the highest implantation potential.
This session is especially relevant for women over 35, over 38, and over 40 who are planning IVF treatment — whether locally or abroad.
Fertility after the age of 38 raises important medical and emotional questions. In this educational session, Dr Silvia Cortell discussed how fertility naturally changes with age and explained how PGT-A (Preimplantation Genetic Testing for Aneuploidy) can support decision-making during IVF treatment.
Before discussing testing or treatment, Dr Cortell emphasised the importance of understanding how fertility naturally changes with age.
Across Europe and globally, women are having their first child later in life. This reflects social progress — education, careers, and personal timing. However, as she explained:
While society has changed, our biology has not changed at the same pace.
Fertility gradually declines over time:
At the same time, the risk of miscarriage increases with maternal age. This is a consistent biological pattern that many patients find surprising.
Women are born with a finite number of eggs, and this number decreases naturally throughout life. As women age:
When Dr Cortell refers to egg quality, she is describing how likely an egg is to develop into a healthy embryo and result in a successful pregnancy.
The most important factor influencing egg quality is chromosomal integrity — whether the egg contains the correct number of chromosomes.
As women get older, the mechanism that ensures chromosomes separate properly during cell division becomes less efficient. This increases the likelihood of chromosomal errors, resulting in embryos with missing or extra chromosomes (aneuploid embryos). As maternal age increases, the proportion of aneuploid embryos increases as well.
This biological reality explains:
Dr Cortell also noted that egg quality involves more than chromosomes. Mitochondrial function and overall cellular health play a role. However, chromosomal health is the most clinically significant factor.
She often reminds patients that even when ovarian reserve appears good, outcomes depend not only on egg quantity but also on egg quality. After 38, reproductive challenges often involve both reduced quantity and reduced quality.
PGT-A stands for Preimplantation Genetic Testing for Aneuploidy.
It is a genetic test performed on embryos created through IVF to determine whether they have the correct number of chromosomes.
Dr Cortell clearly explained that PGT-A:
Its purpose is to provide more information about the embryos already available and help identify those with the highest implantation potential.
This becomes especially relevant after age 38, when a larger proportion of embryos may be chromosomally abnormal.
PGT-A allows clinicians to prioritise embryos based on chromosomal status. For many patients, this additional information is helpful medically and emotionally, as it supports realistic expectations and informed decisions.
Dr Cortell clarified that there are three types of preimplantation genetic testing, each used in different clinical situations.
Focuses on chromosome number (aneuploidy).
Goal: identify embryos with the highest implantation potential and reduce miscarriage risk related to chromosomal abnormalities.
Used when there is a known inherited monogenic disease in the family.
Goal: identify embryos that do not carry the specific mutation.
Used when one parent carries a structural chromosomal rearrangement (such as a balanced translocation).
Goal: reduce the risk of creating embryos with unbalanced chromosomes that could lead to miscarriage or implantation failure.
Although all involve embryo biopsy and genetic analysis, they address different medical questions.
PGT-A requires embryo biopsy.
In earlier years, biopsies were performed on day 3 embryos, which contain only 6–8 cells. Removing one cell at that stage meant removing up to 15–20% of the embryo, potentially affecting development. Testing at this stage was also less reliable.
Today, a biopsy is performed at the blastocyst stage (day 5 or 6).
At this stage:
This makes the procedure less invasive for the part of the embryo that will become the baby and improves the reliability of genetic results.
For these reasons, day 5–6 biopsy is considered the gold standard in modern IVF laboratories.
PGT-A results generally fall into three main categories:
Have the correct number of chromosomes (46).
They have the highest chance of implantation and a healthy pregnancy, although success is not guaranteed.
Contain a mix of normal and abnormal cells.
Outcomes vary depending on the type and degree of mosaicism. Decisions about transfer are individualised and made in collaboration with the genetics team.
Have an abnormal number of chromosomes.
They have a very low chance of leading to a successful pregnancy and are associated with a higher miscarriage risk. They are generally not recommended for transfer.
Dr Cortell outlined several potential benefits:
Genetic information complements visual assessment under the microscope, providing a more complete understanding of embryo viability.
Transferring a chromosomally normal embryo increases implantation chances and may reduce the number of transfers needed. This can be particularly meaningful for women over 38.
Avoiding the transfer of chromosomally abnormal embryos may reduce the risk of early pregnancy loss.
Repeated failed transfers or miscarriages are emotionally difficult. Having more information can help reduce uncertainty and set realistic expectations.
However, Dr Cortell emphasised that PGT-A does not increase the number of embryos or improve their quality. It is a selection tool, not a treatment.
Although advanced maternal age is one of the most common indications, PGT-A is not defined by age alone .
It may also be considered in cases of:
Some patients choose PGT-A even without a strict medical indication because they hope to shorten the time to pregnancy. The decision must always be individualised based on medical history and reproductive goals.
Dr Cortell clearly explained that PGT-A has limitations:
PGT-A also adds cost and laboratory complexity and may increase emotional stress during treatment.
Overall, it is a powerful tool, but not a guarantee.
Dr Cortell concluded with several essential points:
Every patient’s journey is different. The best approach combines medical evidence with individual circumstances, allowing patients to make decisions that align with their goals and values.
Yes, embryo biopsy is an invasive procedure, so there is a possibility of damage. However, this risk is very low. Less than 1% of embryos are damaged during the procedure.
The biopsy is performed by experienced embryologists who handle embryos with great care. The technique is usually performed using a laser, and in the vast majority of cases, there are no problems. Although there is always some risk, the percentage of embryos lost due to the procedure is extremely low.
Patients over 38 are generally already aware of the age-related challenges. When we explain the IVF process, we discuss the risks associated with age and the increased likelihood of chromosomally abnormal embryos.
Many patients understand that PGT-A can help avoid transferring embryos that are unlikely to result in pregnancy. By identifying and excluding abnormal embryos, we can reduce the number of negative transfers and potentially shorten the time to pregnancy. For this reason, many patients both accept and actively request PGT-A.
The decision is based on age, embryo number, reproductive history, and personal circumstances. Ultimately, it is a shared decision between the clinic and the patient.
Reactions vary greatly depending on the couple. We always explain statistics beforehand based on age. However, each case is individual.
Sometimes patients receive very positive results — for example, four embryos and all are euploid. In those cases, patients are very happy.
The more difficult situation is when all embryos are aneuploid. For example, if three embryos are tested and all are abnormal, this is emotionally very challenging. However, many couples understand that knowing this information prevents them from undergoing transfers that would not lead to pregnancy. In that sense, they recognise that they are saving time and avoiding repeated failed transfers, which are also emotionally difficult.
In reproductive medicine, nothing is automatic. Decisions are always made together with the patient after providing full information.
In a 39-year-old woman, we would recommend PGT-A because the percentage of aneuploid embryos at this age is higher. In an ideal world, everyone would perform PGT-A, as it helps avoid negative transfers and shortens the time to pregnancy. However, there are financial considerations.
If a patient chooses to proceed without PGT-A, that is possible, but they must understand the associated risks. The final decision belongs to the patient, based on full information and informed consent.
Non-invasive PGT-A analyses DNA released by the embryo into the culture medium during laboratory development. This avoids embryo biopsy.
However, it is not as reliable as invasive PGT-A. With a biopsy, we are certain we are analysing embryonic DNA. With non-invasive testing, the DNA in the culture medium may sometimes come from the egg cell rather than the embryo.
Over time, reliability has improved. Currently, it has high reliability, but it is still not as accurate as invasive PGT-A.
With invasive PGT-A, we receive a detailed genetic report classifying embryos as euploid, aneuploid, or mosaic. With non-invasive testing, results are often expressed as probabilities. For example, there may be an 80–85% probability that an embryo is normal. However, it is not definitive in the same way as standard PGT-A.
No. PGT-A provides information about chromosomal abnormalities in the embryo. However, not all fetal conditions are related to chromosomes.
For example, structural conditions such as heart defects or kidney abnormalities are not necessarily linked to chromosomal issues. Even if PGT-A confirms that the embryo is chromosomally normal, standard prenatal testing and pregnancy follow-up remain essential.
PGT-A gives information about chromosomes, but it does not replace prenatal screening or ultrasound examinations.
This is a very personal decision.
Clinically, PGT-A is still useful because it allows us to identify whether an embryo is euploid. If one embryo is normal and the other is aneuploid, we can prioritise the euploid embryo for transfer.
Without testing, embryos would be transferred sequentially without knowing their chromosomal status, which may result in more failed transfers.
In women under 35, transferring without testing may be reasonable. However, in women around 40, we usually recommend testing due to the higher rate of chromosomal abnormalities.
It is also important to understand that some aneuploid embryos can implant and lead to pregnancy, for example, in cases like Down syndrome. Therefore, transferring without testing carries not only the risk of failure but also the risk of chromosomal conditions. Patients must be fully informed of these risks.
PGT-A does not improve live birth rates per embryo. If an embryo is euploid, it has the same potential regardless of whether it was tested. PGT-A does not change the embryo.
Its main benefit is shortening the time to pregnancy. By selecting embryos with the highest implantation potential, we reduce the likelihood of negative transfers. Without testing, transferring aneuploid embryos would likely result in failed implantation or miscarriage.
Therefore, PGT-A helps prioritise embryos and avoid unsuccessful transfers, but it does not increase the inherent live birth potential of a euploid embryo.
When mosaic embryos are identified, the genetics team evaluates each case carefully. Some mosaic embryos can be transferred, particularly low-level mosaics. However, certain chromosomal mosaics, such as those involving chromosome 21, may not be recommended for transfer.
Typically, euploid embryos are transferred first. Mosaic embryos are considered only if no euploid embryos are available. The final decision always belongs to the patient.
In many cases where mosaic embryos are transferred following genetic team approval, healthy babies are born. It is important to understand that biopsy samples are taken from the trophectoderm, which becomes the placenta. Sometimes mosaicism may be confined to the placenta, while the inner cell mass — which becomes the fetus — is normal.
However, interpretation is complex and always guided by the genetics team, with full discussion with the patient.
