One critical aspect when determining the success of an in vitro fertilization (IVF) procedure is assessing embryo quality. After the fertilization step, embryologists observe the embryos to recognize which ones will likely have successful implantation and lead to a healthy pregnancy. What some patients may not fully comprehend is what constitutes a “good quality embryo.”
Normal development, healthy appearance, and proper characteristics for implantation are some traits that may contribute to a good quality embryo. Fertility specialists may grade embryos, but that is simply an aid for selecting embryos for implantation and does not guarantee the establishment of a pregnancy. In fact, healthy babies have been born from embryos graded as average, while embryos graded as excellent failed to implant successfully.
In the following, we will discuss the evaluation of good quality embryos within the context of IVF specifically, the methods and levels of embryo grading, the factors that contribute to embryo quality, and the typical expectations for patients undergoing the IVF process.
What is a Good Quality Embryo in IVF?
Embryos that are the product of IVF must undergo an evaluation process if they are to be considered good quality. Healthy growth and development of embryos must be achieved in a laboratory, and the assessment of embryos is the responsibility of clinical embryologists. They will look at the embryos in the days following fertilization through the lenses of development, symmetry, cell division, and overall quality.
Good quality embryos typically exhibit:
– Healthy divisions of cells that are even
– Cell fragmentation that is minimal, if any,
– Proper development with the formation of a blastocyst no later than Day 6
Embryos exhibiting these characteristics will likely continue to healthy development after uterine implantation.
Grading IVF Embryos
Before freezing or transferring embryos, embryologists must check and grade their quality. Grading embryos involves a series of standardized procedures.
What Happens on Day 3 of Embryo Development?
By Day 3 embryos have usually divided into about 6 to 10 cells.
Embryologists check for:
– The number of cells
– Symmetry of the cells
– Fragmentation of the cells
– General appearance of the embryo
A generally favourable embryo at this stage has:
– 8 cells that are equal in size
– Minimal fragmentation of the cells
– Shape of the cells is consistent
Day 5 Embryo Grading: The Blastocyst Stage
Day 5 or 6 embryos are often at the blastocyst stage. Many fertility clinics now prefer to transfer embryos at this stage.
Assessment of the Blastocyst Stage is Done in Three Areas
A. Blastocyst Expansion
This indicates the level of development of the embryo and is typically graded as follows:
– 1 = Early blastocyst
– 2 = Developing
– 3 = Full blastocyst
– 4 = Expanded blastocyst
– 5 = Hatching blastocyst
– 6 = Hatched blastocyst
B. Inner Cell Mass (ICM)
The inner cell mass will eventually develop into the fetus.
This is graded as follows:
A: Many cells that are healthy and compact
B: Moderate amount of cells
C: Fewer cells that are packed loosely
C. Trophectoderm (TE)
The placental tissue will develop from the trophectoderm.
Grades are based on
A: Numerous healthy, identical cells
B: Cells of moderate quality
C: Few or irregular cells
What Makes an Embryo Grade Good?
Examples of high-quality blastocysts are
– 4AA
– 5AA
– 4AB
– 5AB
– 4BA
Generally, they have
– Excellent blastocyst expansion
– An excellent inner cell mass
– A healthy trophectoderm
Embryos graded BB can also have successful pregnancies and many healthy babies are born from average grade embryos.
What Affects Embryo Quality?
In IVF, many things can affect the quality of the embryos.
1. Age
Of the many things that can impact the quality of embryos, the age of the woman giving birth is the most prominent.
Embryos also tend to have more chromosomal abnormalities as women get older. In general, women who are:
– Under 35 years: have good-quality embryos most of the time
– 35–40 years: have a gradual decline in good-quality embryos
– Over 40 years: have a very low percentage of good-quality embryos who are chromosomally normal
2. Egg Quality
Eggs have to be healthy to provide good quality embryos. There are many things that can impact the quality of eggs:
– Health of the ovaries
– Hormones
– Lifestyle
– Health
3. Sperm Quality
Sperm have to be healthy to provide good quality embryos, and poor quality sperm can affect:
– How embryos are formed
– How embryos are developed
– How and if a blastocyst is formed
4. Lab Conditions
Modern IVF labs have very controlled environments.
Embryo quality relies in part on:
– Consistency in temperature
– Culture media
– Quality of air
– Incubator systems
– Skill of the embryologist
5. Genetic Health
Embryos can look excellent under a microscope and still contain chromosome issues.
Some patients do Preimplantation Genetic Testing (PGT) to find and transfer only normal embryo chromosomes.
Do Poor Quality Embryos Have a Chance at Pregnancy?
Yes.
Embryo grading is a way of estimating the chances of implantation; it is not a guarantee.
Some embryos which were graded lower quality have still resulted in successful births. Conversely, higher quality embryos may not implant. These can be caused by:
– Uterine receptivity
– Immunological factors
– Hormonal factors
– Grading genetic factors
Fertility specialists use embryo grading along with the rest of the clinical factors.
Is It Guaranteed That a Good Quality Embryo Will Result in a Successful IVF?
No.
Good quality embryos help ensure a successful pregnancy, but are not a guarantee.
Grading factors such as:
– Uterine environment
– Embryo health
– Maternal health
– Timing of transfer
– Hormonal factors
also help determine the success of the pregnancy.
Is It Possible to Affect Embryo Quality?
Embryo quality has a large genetic factor, which cannot be changed. However, lifestyle choices may help create healthier quality sperm and egg cells for the IVF.
Your fertility specialist may suggest you:
– Manage to your ideal body weight
– Follow a nutrient-rich diet
– Exercise moderately on a regular basis
– Eliminate smoking and limit drinking alcohol
– Manage stress levels
– Get more sleep
– Take fertility supplements when prescribed
Invitro fertilization (IVF) success is likely to improve with better health.
Questions for Your Fertility Specialist
You may have better peace of mind throughout your treatment if you understand your embryo report. You may want to ask your fertility specialist:
– How many embryos were fertilized?
– How many embryos reached the blastocyst stage?
– What are my embryos’ grades?
– What embryo will be transferred and why?
– Should any of my embryos be tested for their genetics?
– How many embryos can be frozen?
Answering these questions may help you with the decision making you will face during your IVF process.
Conclusion
IVF treatment may be easier if you understand what is a good quality embryo in IVF. Consideration of embryo grading is only one of the many important factors that may help you be successful in IVF. Maternal health, the fertility team’s expertise, embryo uterine receptivity, and embryo genetics, are all factors that may help contribute to the success of your IVF treatment.
Better quality embryos are more likely to implant, but many patients are able to achieve a successful pregnancy using an embryo with an average grade. Since every patient’s IVF treatment is different, only your fertility specialist, who you should consult for every treatment decision, is qualified to recommend the best course of treatment for you. Following your specialist’s recommendations and focusing on healthy reproductive improvements will help increase the likelihood of a successful pregnancy.
