When you’re hoping to have a baby, the smallest things can make the biggest difference—even something as tiny as an embryo. If you’ve started your IVF journey, you might have come across terms like euploid and aneuploid and wondered what they really mean. Simply put, these terms tell us if an embryo has the right number of chromosomes, which can play a big role in whether your pregnancy is successful.
We spoke to Dr Rohan Palshetkar, Consultant IVF Specialist, Bloom IVF, Palshetkar Patil Nursing Home, Opera House, who explained euploid and aneuploid embryos, their differences, and how they are diagnosed.
What Are Euploid and Aneuploid Embryos?
“A euploid embryo has the correct number of chromosomes—46 in total or 23 pairs, which is essential for normal growth and development. An aneuploid embryo, on the other hand, has an abnormal number of chromosomes, either an extra chromosome or a missing one,” explained Dr Palshetkar.
Why Does This Matter?
Euploid embryos are more likely to implant successfully and grow into a healthy pregnancy and live birth.
“Aneuploid embryos, however, often lead to lower implantation rates. Even if they implant, they are more likely to result in miscarriage. In rare cases where the pregnancy continues to birth, the baby may have a genetic disorder,” added Dr Palshetkar.
Also Read: World IVF Day 2025: Does IVF Increase Your Chances of Having Twins?
Risk Factors
The biggest risk factor for aneuploid embryos is maternal age. The older the mother, the higher the risk, especially after age 35, when the risk rises significantly.
Other contributing factors include:
- Poor egg or sperm quality
- Lifestyle factors, such as smoking, alcohol, and drug use
- Random errors during cell division
Diagnosis and Testing
The only way to determine whether an embryo is normal or abnormal is through PGT-A (Preimplantation Genetic Testing for Aneuploidy) before embryo transfer. According to a 2025 study, rapid advancements in technology have made PGT-A widely used to identify euploid embryos, reducing risks for patients with single-gene disorders, chromosomal rearrangements, or recurrent spontaneous abortion (RSA). PGT-A categorises embryos as euploid, mosaic, or aneuploid.
PGT-A testing process involves:
- Growing the embryo to Day 5 (blastocyst stage)
- Taking a biopsy from the embryo
- Testing the sample for chromosomal abnormalities
Possible Test Results
PGT-A results typically fall into three categories:
- Euploid (normal)
- Aneuploid (abnormal)
- Mosaic (mixed chromosomal pattern)
What Is Mosaicism?
Mosaic embryos have both normal and abnormal cells. They are classified based on the percentage of abnormal cells:
- Less than 20% mosaicism
- 20–80% mosaicism
- More than 80% mosaicism
Also Read: The Biology Of Sperm Quality In IVF: Why Male Infertility Need No Longer Be A Blockage
Embryo Transfer Decisions
“Usually, as IVF specialists, we transfer euploid embryos. However, if there's a mosaic embryo with less than 20% mosaicism, we still consider it for transfer after thorough counselling. For patients with embryos showing 20-80% mosaicism, we have a detailed discussion about the potential risks and then decide whether to proceed with the transfer. Embryos with more than 80% mosaicism are typically not transferred,” said Dr Palshetkar.
What Are The Limitations?
“Additionally, it's essential to understand that this technology has some drawbacks. “During the biopsy, there's a risk that the embryo could be damaged beyond repair, potentially leading to its loss. Furthermore, false positive or false negative results are possible,” warned Dr Palshetkar. Therefore, if you decide to undergo PGT before embryo transfer, it's crucial to follow up with testing after becoming pregnant to confirm a normal pregnancy. This follow-up testing is a standard part of prenatal care.
Legal Aspect in India
In India, PGT-A is allowed only for medical conditions, as per the law. Couples can avail this technology only if they meet the prescribed criteria.
[Disclaimer: This article contains information provided by an expert and is for informational purposes only. Hence, we advise you to consult your professional if you are dealing with any health issue to avoid complications.]