Why Don’t All Euploid Embryos Result in a Live Birth?

In the past 10–20 years, in vitro fertilization (IVF) has seen incredible advancements. One of the most significant breakthroughs is our ability to successfully freeze embryos at the blastocyst stage and perform genetic testing before transfer. Thanks to this technology, we’ve seen steady increases in success rates, with 60–70% of good-quality euploid blastocyst transfers resulting in a live birth.

During preimplantation genetic testing (PGT-A), we biopsy a few cells from the trophectoderm—the part of the embryo that will eventually become the placenta—to assess whether the embryo has the correct number of chromosomes. We know that having a normal number of chromosomes is the strongest predictor of a successful embryo transfer. We also know that as women age, the chance of producing a chromosomally normal embryo declines due to age-related changes in egg DNA.

So why don’t all euploid embryos result in a live birth?

While genetic testing has been a tremendous advancement, it’s not the whole story. Several other factors can affect the outcome of an embryo transfer:

Limitations of Genetic Testing

Because DNA replication is very inefficient in the early stages of the embryo, there is often DNA damage and chromosomal breaks which affect the competence of the embryo. PGT-A is designed to detect large-scale chromosomal abnormalities—whole chromosomes or large segments that are missing or duplicated. However, it cannot identify small DNA mutations that may impact embryo development. It is often these single gene mutations that can render an embryo nonviable (which would be missed by our genetic testing). It also doesn’t assess the embryo’s metabolic or cellular function, both of which are crucial for healthy growth and implantation. In addition, the genetic testing platform itself is not perfect and has an error rate of approximately 2%.

Sampling Limitations

The biopsy used for genetic testing samples the trophectoderm, which is genetically very similar to the inner cell mass (the part of the embryo that becomes the fetus). Still, it is possible that the inner cell mass contains undetected abnormalities that are not present in the sampled cells.

Other Influential Factors

Even with a chromosomally and genetically normal embryo, other elements may rarely influence implantation and development. Uterine environment, immune factors, and hormonal imbalances may all play a role. If you've experienced multiple failed transfers, your doctor may explore additional testing to investigate these potential issues.

Recurrent implantation failure is almost always caused by the embryo and much less likely by issues pertaining to the person carrying the pregnancy.

Statistical Reassurance

While no single embryo transfer can guarantee success, data shows that most patients with three genetically normal embryos have a 95% chance of achieving a live birth. This is an encouraging statistic that speaks to the power—but also the limitations—of embryo genetics.

Final Thoughts

The embryo is often the most critical piece of the puzzle, and your best chance of success comes from working with an IVF center that has a high-quality laboratory and expertise in genetic testing in embryos.

IVF is often a marathon, not a sprint—but we’re here to guide and support you every step of the way.

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