When undergoing an IVF cycle, not all embryos develop at the same pace.

While slower development can sometimes be a cause for concern, it’s important to understand that not all slow-growing embryos are destined to fail.

Once your embryos are developed, we can help you find a surrogate. Contact us today to start your journey.

In this article, we’ll explore the factors that contribute to slower embryo growth, whether these embryos can catch up, and what it means for the success of your IVF journey.

If none or few embryos become viable for transfer, read more about your next steps.

Can Slow Growing Embryos Catch Up?

Yes, a slow growing embryo can catch up. Embryo growth is typically assessed at day 3 and day 5 (blastocyst) of development during an IVF cycle.

Embryos developing slowly at day 3 have the potential to grow and reach full blastocyst development, especially with additional time to culture in the lab.

A slow growing embryo can be associated with less than ideal treatment outcomes, but most clinics will still freeze them for later use.

Read more about success rates of day 3 embryos.

How Many Cells Should a Day 3 Embryo Have?

On day 3, embryos typically should have divided into at least 6-8 cells. If the embryo has the appropriate number of cells and is dividing normally, it is considered to have a higher chance of progressing to the next stage—the blastocyst stage.

If it has fewer cells, it may be categorized as a slow-growing embryo.  

However, embryos with fewer than 6 cells, such as those with 3, 4 or 5 cells, can still have the potential to develop into a healthy pregnancy.

Can a 3 Cell Day 3 Embryo Catch Up?

Yes, a 3 cell day 3 embryo can catch up. Although 6-8 cells are the average number by day three, embryos with as few as 3-6 cells can still develop into a healthy fetus.

Can a 4 Cell Day 3 Embryo Catch Up?

Yes, a 4 cell, day 3 slow growing embryo can catch up. Although the chances of success are lower than a faster growing embryo, additional time to culture can allow it to catch up developmentally.

Can a 5 Cell Day 3 Embryo Catch Up?

The number of cells is a good indicator of its chance to develop into a healthy pregnancy. An embryo with five cells can catch up.

Can a 6 Cell Day 3 Embryo Catch Up?

Yes, a six cell day three embryo can catch up development wise. With 6-8 cells being the average number of cells by day three, it’s well within the range to “catch up.”

How Many Day 3 Embryos Make It to Day 5?

On average, 30-50% of day 3 embryos make it to the blastocyst stage on Day 5. This number can vary depending on various factors like embryo quality, age, and laboratory conditions.

What Are the Reasons for Slow Growing Embryos?

Slow growing embryos can occur for a number of different reasons such as:

• Egg Quality: Age directly impacts the quality and quantity of eggs. Issues with ovarian stimulation or mitochondrial dysfunction can also impact the energy that fuels normal embryo development.
• Underlying Health Conditions: This could range from the intended mother having polycystic ovary syndrome, leading to egg that don’t develop normally, or lifestyle factors like smoking, obesity, stress and more that can affect the quality of gametes and therefore development.
• Sperm Quality: Poor sperm motility contributes to impaired fertilization and early development. Damage to the DNA in the sperm can result in slower growth for embryos too. 
• Embryo Culture Environment: Your choice of professional directly impacts your journey. A laboratory with variations in different aspects like temperature, oxygen concentration and more can impact embryo growth negatively.
• Genetic Abnormalities: An incorrect number of chromosomes after dividing abnormally or genetic mutations that impact the cellular processes around normal development, genetic abnormalities can result in slow-growing embryos.

Are Slow Growing Embryos Female?

According to this paper from the National Library of Medicine, there was no difference in day 3 embryos in embryo transfers that resulted in male vs. female infants.

Slow Growing Embryo Success Stories

If you are concerned about whether slow growing embryo can catch up or not, there are plenty of success stories out there.

One intended mother posting on r/IVF on Reddit had 15 egg retrieved, 12 matured and 10 fertilized  On the fifth day, she was told all 10 were developing slower than normal and hadn’t yet reached the blastocyst stage.

Another user in the top responses had a similar situation resulting in success.

“All of my embryos were slow growing. I only made day 6 and 7 embryos,” replied the user. “My clinic told me day 6 are their most common. I am not sure if the embryos I transferred were day 6 or 7 but both of my transfers worked and I have a 19 month old and am 16 weeks with our second.”

When your embryos make it to the next stage, you’re one step closer to bringing your family dreams to life through surrogacy.

Contact us today to start your journey and get matched with surrogate who aligns with your needs.