Overview
You must know that embryos are created in IVF cycles, but do you know how many? This article will help you figure out these numbers. Additionally, it explains how these embryos are formed in IVF, the factors that influence this process, and what happens to the leftover embryos. So let’s get started!
What Is an Embryo in IVF?
In IVF, an embryo is formed with the combination of sperm and egg, termed as fertilisation, in a controlled laboratory setting. After the fertilisation, the fertilised single cell starts to divide, forming an accumulation of divided cells that grows over the next 3 to 5 days.
Note that in IVF, more than one embryo is created, unlike in a natural setting, where typically only one embryo is formed. To simplify, here is the flowchart:
Egg → Fertilisation (Egg+Sperm) → Embryo
This stage is the foundation of life; therefore, in IVF, it is thoroughly monitored by embryologists to identify the healthiest embryos to transfer.
How Many Embryos Can Be Created in IVF?
The number of embryos created in an IVF cycle is not fixed. That is, it can vary based on several different factors. So the question: how many embryos are created in one IVF, is best answered by the following influencing factors:
- Number of Eggs Retrieved: A larger number of eggs stimulated means more eggs being retrieved, which typically increases the embryo count as well.
- Egg Quality: In IVF, the quality of an egg can not be compromised for further processing. So, less healthy eggs will result in fewer embryos created.
- Sperm Quality: Just like eggs, sperm quality is also verified before fertilisation, and those with poor quality are processed out, eventually reducing their ability to fertilise the egg and form an embryo.
- Lab fertilisation success rate: Advanced lab facilities and the skills of an embryologist can also determine the success of embryo formation in the lab.
Here’s a rough estimate of how many embryos are formed in some standard cases:
| Egg Retrieved | Fertilised Successfully | Embryos Available |
|---|---|---|
| 10 | 8 | 6–7 |
| 6 | 5 | 3–4 |
How Many Embryos Come from One Egg?
For “How Many Embryos from One Egg”, then the answer is only one, that too when the sperm fertilises the egg normally and continues to develop.
However, in extremely rare cases, a single embryo can split into two or more identical ones, resulting in identical twins. Note that this is a natural process, and no fertility treatment (IVF/ICSI) can help you achieve it.
For the context, we must also know the difference between a fresh and frozen embryo. In the former, the embryo is prepared and used in the same IVF cycle, but in the latter, the preserved embryos are used from either prior cycles or donated.
Factors Affecting Embryo Creation in IVF
Embryo creation in IVF is not an isolated procedure; rather, it depends upon several different factors, some of which include:
- Age of the woman: As we know, fertility declines with increasing age. In women, this occurs due to declining egg quality, which directly affects the rate and reliability of eggs being fertilised.
- Ovarian Reserve: It is the number of eggs left in the ovaries. A decreased reserve means fewer eggs are available to be stimulated and mature during IVF, which eventually reduces the probability of embryo formation.
- IVF Technique: In cases of severe male infertility, ICSI with IVF can provide better success rates at fertilisation and eventually embryo development than conventional IVF.
- Lab conditions: The modernity of the lab facilities will also determine how proficiently embryos are created.
What Happens to Extra Embryos?
An IVF cycle typically produces more than one healthy embryo, but not all of them are used in one go. These extra embryos, if permitted and requested by the patient, are preserved through embryo freezing or cryopreservation. This is a gem of medical science, using liquid nitrogen to freeze these embryos, giving the remaining embryos a second chance at life.
Using these frozen embryos has its own ethical and medical considerations. For example, couples can choose to store embryos for the long term, donate them for research and any donor program, or destroy them as per clinical guidelines.
In numbers, frozen embryo transfers offer a success rate of about 24% overall, a bit less than fresh ones, but still a good one.
Conclusion
Ultimately, we can conclude that the number of embryos created per IVF cycle varies for each individual. Rather, it can differ from one individual to another, depending on the quality of the egg, sperm health, age, and even lab expertise. What matters most is the strongest embryo to thrive in the uterine environment for about nine months. You can talk to our IVF specialists at Indira IVF to understand how many embryos you might create in your IVF cycle and receive a personalised plan for beating infertility.
Common Questions Asked
Is IVF successful with one embryo?
IVF with one high-quality embryo, particularly a Day-5 blastocyst, can yield very good success rates. Many clinics offer elective single embryo transfer (eSET) as part of their strategy to promote safety while maintaining excellent pregnancy rates.
Can one IVF embryo be twins?
Yes, this is very uncommon. A single embryo can result in twins if it splits naturally after transfer, as these are genetically identical twins. This occurrence occurs naturally and is unrelated to any IVF process or clinical recommendation.
What does "single embryo" mean?
A "single embryo" means transferring a single embryo to the uterus during an IVF cycle. The intent is to achieve safety for the pregnancies produced while minimising the possibility of multiples or, in some cases, multiple pregnancies.
Why did the second IVF with two embryos fail?
When two embryos are transferred, success can never be guaranteed. The chance that the second cycle would have been successful is always uncertain. Embryo genetics, embryo quality, uterine lining health, immune system factors, natural sperm factors or failure of the embryo to implant may have anything to do with success.