Guide to IVF Lab Results: Embryo Grading System & FAQs

Posted on June 27, 2024

What to Expect While Your Embryos Are in The IVF Laboratory

The laboratory component of your IVF journey should not be mysterious, and we always welcome your questions. The science behind growing embryos in vitro is constantly evolving as we strive to make the culture environment as natural as possible to optimize your chance of success. It is now standard practice to grow embryos for 5 or 6 days before transfer and/or freezing (when they will have reached the “blastocyst” stage) as this has some very important advantages:

  1. Growing embryos for 5 days instead of 3 is an excellent selection tool: only a proportion of embryos will become blastocysts, the others will stop growing.
  2. If the embryo becomes a blastocyst, it has a much higher chance of implanting. This means fewer embryos can be transferred to achieve a healthy pregnancy, and the risk of multiples is subsequently reduced. It also allows us to eliminate poorer quality embryos which would not have made a pregnancy.
  3. For successful implantation, the stage of the embryo and the lining of the uterus must be “in sync”, and this is more easily achieved when the embryo is at the blastocyst stage, matching more closely with what happens in a natural cycle. At PCRM we have a reliable, reproducible culture system, and because of this we are happy to grow everyone’s embryos to day 5 before transfer. There is no way to know for sure whether all embryos that fail in culture would also have failed in utero, but we believe that there is no harm caused to your embryos by five days of growing in the lab.

What follows is a brief outline of what will be happening to your embryos for the six days that they will be in the lab.

When Will I Get an Update?

We will NOT provide any updates on day 2 or day 3.

Do You Grade The Embryos?

Yes! From day 1 to day 4, we score cleavage embryos on a scale from 1 - 5.
1 = excellent
2 = good
3 = average
4 = a little below average
5 = below average (poor).

If embryos are graded 1-3, we are happy with their quality. If they are graded 4 and 5, we will caution you that those will likely have a lower chance of becoming blastocysts. The most important thing is that there is daily progression of the embryos. However, if an embryo is too far behind the ideal time points that we look for, it is less likely to be successful in causing a pregnancy. It is perfectly normal to have a mixture of embryo stages and grades, especially when you have a larger number of embryos.

Once the embryo becomes a blastocyst on day 5 or on day 6, its score describes the parts of the blastocyst, and consists of a number followed by 2 letters (for example 4AA). This scoring system and what it means will be fully explained to you before your transfer. Like most IVF Clinics, we use the Gardner Grading System for blastocysts. Read further in this booklet to see a visual explanation of both the cleavage and blastocyst grading system.

Embryo Transfer – Important Instructions

You will be given your transfer time when we send you a message through the Prelude Connect App on day 4. Transfer time is usually mid to late morning. Please remember to arrive at PCRM 30 minutes before the scheduled time. Take your medications as you normally would on the morning of your transfer, and make sure that your bladder is comfortably full - this will make it easier for the Physician to have a clear picture for your ultrasound-guided transfer. Drink 3-4vglasses of water 1-2 hours before the scheduled transfer time.

Will You Freeze Surplus Embryos?

On average, we expect around 50% of good quality day 4 embryos to develop into blastocysts (remember, this is an average for ALL patients therefore, some patients will have more embryos to freeze, and some may have less). On average, we freeze 70% of blastocysts. Blastocysts must be of good quality, or they will not survive the freezing or thawing processes. We will not freeze blastocysts of poor or sub-optimal quality, as they are not likely to survive.

What if my Embryos Are Not Blastocysts on Day 5?

Sometimes embryos will not have reached the blastocyst stage at the time of your transfer on day 5- Do not worry, this happens often. If your embryos continue to grow each day, we will still transfer one or two of the most advanced embryos and grow all the others for one more day. You will receive a final message through the Prelude Connect App from the Laboratory on day 6 to inform you of any embryos that were frozen. Freezing can be done on day 5 or on day 6 – we wait until the blastocysts have developed the ideal number of cells before we freeze it.

On Day 4, How Do You Estimate How Many Embryos Will Be Frozen or Biopsied?

All of our Embryology staff have experience in estimating blastocyst formation numbers, using both clinic statistics and by observing how your embryos have developed over a four-day period. The estimate is based on our conservative “educated guess” and is the best estimate we can give at the time. The number being frozen or biopsied may end up being more or less than what we have estimated. If you are having a “freeze all” cycle, or a PGT cycle, we will not update you on day 5, but we will update you sometime on day 6 with a final update.

Experience Exceptional IVF Support & Guidance at PCRM

IVF is a beautifully complex procedure, one that PCRM strives to demystify as much as possible for our patients. We believe that a comprehensive IVF journey needs to ensure that all aspects of laboratory components and the embryo grading process are easily understood and accessible. Thanks to our Prelude Connect App, we can easily communicate with patients about any embryo updates, including embryo development, images, and more. We’re also here to provide patient education and address all questions and concerns about embryo grading or any other aspect of the IVF process. For an exceptional IVF and fertility clinic experience in Burnaby and Victoria, British Columbia, connect with PCRM today to request a consultation.

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Disclaimer: The information on this page applies only to PCRM’s Burnaby and Victoria fertility clinics.

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About the PCRM Blog

Welcome to the Pacific Fertility Centre for Reproductive Medicine Blog! Nationally and internationally recognized for providing exceptional reproductive care, our team believes in empowering people with the knowledge they need to navigate their unique fertility journeys.

From information on the latest fertility treatments to valuable insights on egg donation, surrogacy, and everything in between, the Pacific Centre for Reproductive Medicine Blog is your ultimate resource for all things reproductive care and support. Read on to learn more, and contact us today if you have any questions or want to schedule a new patient appointment.