Everything you wanted to ask an embryologist: part one

The role of an embryologist is central to the success of an IVF cycle, requiring an exceptionally high level of skill and focus to nurture life at its earliest stages. However, embryologists don’t only work in the laboratory; they also regularly communicate with patients, helping them understand the lab side of their treatment.

Kim Hill, Senior Clinical Embryologist at Aria Fertility, answers the questions they get asked most frequently: “We try to guide the patients through the decisions they will have to make, help them understand what to expect in terms of outcomes, and manage their expectations.

My embryo was abnormal; why did you freeze it?

Even embryos that look good in the lab and have good grading may have defects not visible to the naked eye.

If an embryo undergoes PGT-A testing, we must freeze it while we wait for the results. When the embryo is grown to the blastocyst stage, we do the biopsy procedure, where we remove a few cells, but then we must freeze the embryo while we wait for those test results, which can sometimes take about two weeks to come back.

Another reason would be that the patient wishes to test embryos further. So, if the embryo was frozen and they wish to do genetic testing at a later stage, then we would thaw the embryo, biopsy it, and then refreeze it. Unfortunately, it could then come back as abnormal.

How long do frozen embryos last?

From a biological standpoint, embryos preserved through modern vitrification techniques can be maintained indefinitely, provided they remain frozen. We know that quality doesn’t decrease, and survival rates are good.

Legally, the current rule is that gametes or embryos can be stored for up to 55 years, but you will need to renew your consent every ten years. Some patients choose not to consent for the full ten years, so we must go through the renewal process with them and discuss their options at an earlier stage.

What is the likelihood of embryos not surviving the thaw?

Unfortunately, it does happen, although not very often. Our in-house survival rates are about 98% and so we are confident in our freeze and thaw protocols. Thorough training is involved to reach competency and this is important to maintain that high rate.

The embryo grade is a description of how robust it is to survive the freeze and thaw processes.. If an embryo is only borderline quality, we must discuss it with the patient(s) so they understand it might only have lower survival rate. It’s about clear communication and an empathetic approach with the patient.

We have a cut-off criterion for embryos, and we are as transparent as possible. Our role is to ensure patients have all the information they need to make this decision. Every patient’s journey is different, so it is never a one-size-fits-all situation.

Are frozen transfers more successful than fresh ones?

Our rates are pretty similar between fresh and frozen transfers. A fresh transfer means they collect the eggs, quickly followed by the implantation, which is a lot for the body to go through. Whereas a frozen transfer means you can let your body recover after the stimulation cycle.

Is the size of the follicles linked to egg/embryo quality?

It’s difficult to predict which eggs will come from which follicles. In general, you are more likely to expect more mature eggs from bigger follicles, but sometimes they can be empty, and sometimes we get mature eggs from smaller follicles as well. Our doctors always aim to get as many eggs as possible.

How do you grade embryos?

We get a lot of questions about this because we give our patients a report which outlines the quality of the embryos. Aria employs the Gardner Grading Scale, the most common and universally used blastocyst grading system.

It has three parts: the expansion of the embryo, the Trophectoderm (TE) layer quality, and the inner cell mass (ICM) quality.

This means that at your blastocyst-stage, depending on how expanded the embryo is, you can usually see the two cell types. The trophectoderm is the outer cells, which become the placenta, and then you have the inner cells, or the baby-making cells.

The Gardner Blastocyst Grading System:

Number (1 to 6)- Blastocyst development stage – expansion and hatching status.
First letter (A to C)- Inner cell mass (ICM) quality.
Second number (A to C)- Trophectoderm (TE) quality.

Aside from grading, how do you choose which embryo to transfer?

If a patient has multiple embryos of similar quality and hasn’t been tested for genetic status, we use a few scoring systems.

AI algorithms are built into our embryoscope, our time-lapse incubator. We use the KIDScore™, which tells us the embryo’s potential for implantation based on a large amount of data from multiple clinics. We also have something called the iDAScore, which predicts the chance of achieving a clinical pregnancy based on the detection of a foetal heartbeat.

We also use the ERICA (Embryo Ranking Intelligent Classification Assistant), an AI system that ranks embryos based on their chance of being euploid or genetically normal.

Our success rates are based on the clinical data we’ve collected over the years, and these multiple systems are tools for applying this data quickly to help with embryo selection.

If we’re doing a fresh transfer, you have to make the decision relatively quickly (day 5 of embryo development). If it’s a frozen transfer, you have from the point they start taking their luteal support medication, so we have a couple of days to decide. We usually have a team discussion, and we also like to consider the patient’s choice.

More questions? Call +44 (0) 203 263 6025 or email us at admin@ariafertility.co.uk to arrange a consultation at Aria Fertility.