31/05/2026
One of the most difficult conversations in IVF is explaining why an embryo that looked perfectly fine on Day 3 did not make it to Day 5.
Many patients assume that once fertilization happens, embryo development is guaranteed. But embryology is far more complex than that.
An embryo’s journey involves multiple developmental checkpoints. One of the most important happens around Day 3, when the embryo stops relying primarily on the egg’s stored energy and begins activating its own genetic material. This is when DNA from both the egg and s***m must start working together to direct further development.
Sometimes, despite everything appearing normal initially, the embryo may carry chromosomal abnormalities or genetic issues that prevent it from progressing further. In these cases, development naturally stops.
While this can be disappointing, it is important to understand that embryo arrest is not uncommon. In fact, a significant proportion of embryos do not reach the blastocyst stage, even in well-managed IVF cycles with excellent laboratory conditions.
This is also why IVF is a numbers game to some extent. Not every egg becomes an embryo. Not every embryo becomes a blastocyst. And not every blastocyst will be chromosomally normal.
But every stage gives us valuable information.
As fertility specialists, we don’t just look at the embryos that stopped growing. We look at the pattern, the timing, the egg quality, s***m health, age-related factors, and everything else that helps us understand the bigger picture and optimise future outcomes.
Because behind every embryo is a story, and behind every IVF cycle is a team constantly trying to understand how to improve the chances of success.
Save this post if you’ve ever wondered why some embryos stop developing after Day 3.
[embryo arrest, IVF, blastocyst development, embryo growth, embryology, IVF education, fertility treatment, s***m DNA fragmentation, egg quality, embryo development, fertility awareness, assisted conception]
