Everything you wanted to ask an embryologist: part two

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Embryologists perform an essential role throughout the patient pathway at an IVF clinic. As well as their lab work, they also regularly interact with patients. In part two of ‘Ask an Embryologist’, Senior Clinical Embryologist Kim Hill answers your most frequently asked questions, including how often you will hear from your embryologist.

“We speak to patients in general every other day, typically after the fertilisation check, then on day three and day five. Obviously, some people prefer not to hear from us during that time and just want to know the final outcome, which is fine. Some people want to speak to us every day. It depends on how the patient feels and what support they need.”

What is the difference between a day three embryo and a blastocyst?

At day 3, it should have about six to eight cells. When it becomes a blastocyst, it makes different cell types and expands. You can usually start to see a small cavity forming by the end of day four, and by day five, you would hope to see a nicely expanded blastocyst with clear cells inside. It usually reaches that stage on day five or day six, but it can even be from day 7.

Why do so many embryos stop growing after day 3 and not make it to day 5?

Most fertilised embryos reach the day 3 stage, as the egg drives development until that point. The drop-off from day 3 to day 5 is when the egg and sperm fuse, creating a new genome. This process requires a lot of energy.

If it reaches the blastocyst stage, we know it’s overcome a major hurdle in the embryo’s growth.

Only about 40 to 50% of embryos make it from fertilisation to day 5 stage, so it is essential to prepare patients for this.

Is there anything that could address this in the future?

Unfortunately, IVF is a numbers game, which is why the patients go through the stimulation process because we want to start with as high a number as possible.

Techniques will hopefully be developed in the future to address that drop-off. Artificial Oocyte Activation (AOA) with Calcium Ionophore is currently being investigated, although more research is required to determine its benefits for patients.

When my embryologist talks about normal fertilisation the day after my retrieval, what does that mean?

A newly fertilised embryo will have one small circle for the egg and one small circle for the sperm. That is what we call a Pronuclear (2PN) embryo. Sometimes, you can get a 1 PN or 3 PN embryo, and this usually indicates that something isn’t right. For example, three circles could indicate that two sperm fertilised the egg at the same time during IVF, which means there is too much genetic material in there, and it’s likely that that embryo will be abnormal.

What is assisted hatching?

Assisted hatching is a technique that we use to help the embryo hatch out of its hard outer shell. When the embryo is small, it has a thick layer of protein around it and when it’s ready to implant, it normally hatches out of this shell.

A small incision is made using a laser. Sometimes, we may do this if the embryo can’t hatch naturally, but often, we do it if we need to do a biopsy. At that point, the embryo is hundreds of cells, and this helps us get a couple of cells from the outer layer with the least manipulation as possible.

What is PGT-A?

PGT-A is pre-implantation genetic testing for aneuploidy, and more and more patients are opting for it compared to three to five years ago. It checks the number of chromosomes inside the embryo.

The Aria consultant will discuss this with them initially but often they are receiving a lot of information at this stage, so we will also discuss this with them during the decision-making process.

Can my embryo be damaged during the PGT biopsy process?

Anything that requires embryo manipulation is risky, but I would say the risk here is very low, under 5%. The process requires us to remove three to five cells from the embryo, but at this point, it has hundreds of cells, and we know it can regenerate those cells quickly as long as the quality is sufficient.

It requires quite a bit of training on our part because you are taking cells from the outside, which are the placenta cells, rather than the inner cell mass.

How is sperm quality assessed?

Sperm quality is taking a front seat compared to ten or fifteen years ago. There has been a decrease in sperm count worldwide, and there has been much research into the role of lifestyle factors, such as our sedentary lifestyle, diet, stress, and pollution.

We assess the sperm under a microscope, looking at the number of cells we can see, how they move, and how they look. We use certain criteria to determine whether we can proceed with IVF confidently, knowing that there’s a good chance of fertilisation.

If it doesn’t quite meet those criteria, we recommend ICSI, which bypasses the swimming process.

How much does sperm DNA fragmentation affect the quality of embryos?

Sperm DNA fragmentation is linked with poor embryo development and quality and is being taken more seriously now. We can perform a test to determine the damage or ‘fragmentation’ of the strands of DNA held inside the sperm head. This can be genetic but can also be caused by several factors, including lifestyle choices, environmental factors, and health issues.

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

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Everything you wanted to ask an embryologist: part one

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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.

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Is a vegetarian diet good for fertility?

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It’s National Vegetarian Week, and the latest figures show there are just over 3 million vegetarians and vegans, with 4.5% of the UK population having a vegetarian or vegan diet.

Traditionally, meat was the star of a meal, but more and more of us are cutting back or cutting it out together, whether you’re a ‘classic’ vegetarian, lacto or ovo vegetarian, pescetarian or flexitarian. The health benefits of a vegetarian diet can be myriad, from boosting heart health, lowering blood pressure and cholesterol, preventing diabetes and managing your weight to keeping your brain sharp and reducing the risk of cancer.

In our latest blog, we focus specifically on whether a vegetarian diet is good for fertility and explore how other popular diets, ranging from keto to vegan, affect fertility and IVF outcomes.

Does vegetarianism impact your fertility?

The first question should be, does diet affect your fertility? The reasons that couples are unable to conceive range from a woman’s ovaries not producing healthy eggs or blocked fallopian tubes that prevent the egg from moving to the womb to the egg’s inability to attach to the lining of the womb successfully. Male infertility can be the result of poor sperm quality, including motility, morphology and sperm count.

Even after tests, the cause of infertility may not always be clear, as about 15% of infertility cases remain unexplained.

No individual food or supplement can fix these potential issues, but there have been multiple studies into the positive and measurable influence of diet and other related lifestyle choices on fertility.

If done correctly, a vegetarian diet is at least as healthy as one that involves meat. It is important to clarify that any diet—whether plant-based or meat-focused—must be well-planned and varied in terms of nutrients and avoid ultra-process food (UPF). The popularity of plant-based meat alternatives has seen staggering growth in recent years.

In fact, it might be even better, as a 2015 study into IVF couples found that men’s meat consumption could affect the outcome of fertility treatments. Although poultry consumption had a positive impact, processed meats such as bacon and sausage, with men who ate the most processed meats, with an average of 4.3 servings a week, had just a 54% chance of achieving pregnancy with their partner.

What about other popular diets?

A recent study published in Nutrients journal examined the impact popular diets have on fertility. It analysed the Mediterranean diet, the DASH diet, the keto diet, and plant-based diets such as vegetarianism and veganism.

  • Mediterranean diet: Rich in fruit, vegetables, nuts, whole grains olive oil and other heart-healthy fats, this diet is routinely described as the gold standard for health and there is growing evidence it could also be beneficial for fertility.
  • Dash diet: This diet was devised to lower blood pressure. It heavily features fruit, vegetables, and nuts with low meat and salt consumption. It’s been found to be beneficial for PCOS patients.
  • Vegetarianism and veganism: Excluding meat and potentially all animal products, these diets can have many health benefits but could cause nutritional deficiencies if poorly planned.
  • Ketogenic diet: high fat and low-carb diets have proven very successful in diabetes management or reversing obesity and have also shown significant benefits for women suffering from PCOS.
  • Western diet: high in ultra-processed foods and chockfull of sugar and salt, this diet is linked with rising BMIs and associated health risks. Studies have also shown a negative impact on sperm quality and embryo development.

If you’re looking for more advice on nutrition and fertility, please visit our Support Hub, where we provide links to experienced and empathetic dieticians who treat couples and individuals undergoing fertility treatment. To arrange a consultation with one of our fertility experts, call +44 (0) 203 263 6025 or email admin@ariafertility.co.uk.

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Veganuary: can a plant-based diet affect your fertility?

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First launched a decade ago, the Veganuary campaign had convinced half a million people to adopt plant-based eating by January 2021, almost double the number that had pledged to go vegan for January in 2019.

According to the Sainsbury’s Future of Food report, vegetarians and vegans will make up a quarter of the population by 2025. Individuals adopt a vegan diet for various reasons, including concerns about the environment, animal welfare, and personal health. While reducing animal product intake has proven health benefits, complete elimination may pose risks of nutrient deficiencies, potentially affecting fertility.

What are the pros of a vegan diet for fertility?

  • Eating plant-based foods means an increased consumption of fruits, vegetables, whole grains, nuts, seeds, legumes, and beans that can positively impact fertility, providing essential nutrients such as antioxidants, fibre, and B vitamins.
  • Increased vegetable protein intake by opting for plant-based proteins like beans, legumes, tofu, tempeh, nuts, seeds, and whole grains, instead of animal protein. This may reduce ovulatory infertility
  • Better gut health: A well-planned vegan diet rich in fibre supports healthy digestion and contributes to a balanced microbiome. This, in turn, may regulate hormones associated with fertility-related conditions.

What are the cons of a vegan diet for fertility?

  • Consumption of vegan ‘junk food’ – although these products may be marketed as healthy alternatives, many vegan options are highly processed, containing excess salt, preservatives, and fewer vitamins and fibre. Quality, rather than mere balance, is crucial for fertility.
  • A poorly planned vegan diet can result in nutrient deficiencies, and this is potentially the most significant impact on fertility. Common nutrient deficiencies in a vegan diet include vitamin B12 and iron. Iron from plant sources is poorly absorbable, and a deficiency can affect both male and female fertility. Vitamin B12, found exclusively in animal products, plays a crucial role in DNA production. Deficiencies in these nutrients can negatively impact fertility.

Current research doesn’t conclusively support the idea that eliminating animal products positively influences fertility. Some studies even suggest potential benefits of certain animal products, like dairy, in female fertility. Therefore, adopting a well-balanced diet containing both plant and animal products may be a prudent approach.

Other steps to take include supplementation of essential nutrients, embracing fortified products and enhancing iron absorption by pairing iron-rich vegetables with vitamin C-rich foods or supplements which can aid absorption.

Please visit our Support Hub for information on Fertility Nutritionists that can give you advice on a vegan-friendly fertility diet plan. If you have more questions about preparing for your fertility treatment, call +44 (0) 203 263 6025 or email us admin@ariafertility.co.uk on to book a consultation.

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Answering your egg freezing questions

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Egg freezing provides a unique opportunity to protect your fertility potential and it is becoming an increasingly popular and effective treatment option to preserve your eggs until you are ready to start a family in the future.

If you are contemplating egg freezing, it’s essential you are fully informed about the steps involved and the potential benefits as well as possible drawbacks. Here are just some of the questions we commonly get asked about egg freezing.

What is egg freezing?

Egg freezing is a process in which eggs are retrieved from the ovaries and cryopreserved for possible use later. As fertility declines as you age, your chances of achieving a successful pregnancy will be similar to the age you froze your eggs.

Why should you consider egg freezing?

Today, more and more women are delaying starting a family until later in life due to personal, social or career circumstances. As techniques and technology continue to evolve, egg freezing has become an increasingly popular method of preserving fertility, as freezing your eggs at a younger age may offer a better chance of a successful pregnancy.

How are eggs frozen?

Once the eggs are retrieved from the ovaries, they are assessed, and mature eggs are frozen soon after retrieval in a technique known as vitrification. This flash-freezing method means water molecules do not have time to form ice crystals, resulting in less damage when the eggs are thawed.

What can I expect during the egg-freezing process?

The egg-freezing journey typically takes approximately 14 days. As we want to collect as many mature eggs as possible per cycle, the ovaries are stimulated with hormone injections. We will perform scans and blood tests to monitor the progress so we can time the trigger injection. Egg collection is then timed for approximately 36 hours after this time.

What can I expect from the egg retrieval process?

Egg collection is done transvaginally in much the same way as a transvaginal scan. The procedure typically takes 30 minutes under mild sedation. Your eggs will be collected using a needle that goes into each ovarian follicle and uses gentle suction to pull out the fluid which contains the egg.

Once rested, you should be able to return home after a couple of hours. You may experience tiredness, bloating, mild abdominal pain and light vaginal bleeding for a few days after your procedure. Most patients can resume their regular routine the next day.

Is egg freezing painful?

Some elements of the egg-freezing process can be uncomfortable, depending on your sensitivity. However, the experience is not painful for most women.

The hormone injections can sting a bit, but your nurse will advise on how best to administer these injections. During this time, you can feel very bloated and crampy, varying from patient to patient.

Your egg retrieval will be performed under sedation so you will not feel anything, but afterwards, you may experience some mild abdominal pain and a little soreness.

What are the risks of egg freezing?

Egg freezing is considered a relatively safe, low-risk procedure. One potential risk is ovarian hyperstimulation syndrome (OHSS).

Stimulation of the ovaries is a deliberate aspect of egg freezing, as we try to obtain as many mature eggs as possible. When the ovaries are stimulated, there is a possibility of OHSS developing, which is an excessive response to the drugs used to encourage multiple follicles to form.

Most cases of OHSS are mild to moderate, occurring in up to 5% of all patients undergoing IVF treatment. This can give symptoms such as mild abdominal discomfort and nausea and usually settles with painkillers and maintaining a good fluid intake.

Very occasionally, OHSS can be more severe, causing marked swelling of the abdomen, dehydration, nausea and vomiting and difficulty in breathing. This is uncommon and may happen in up to 1% of women undergoing ovarian stimulation.

The team will manage the risk of OHSS, which might include altering the dose of stimulation medications or using a different trigger injection.

How many eggs should I freeze?

The success of techniques like IVF is dependent on two main factors: the age at which treatment takes place and the number of eggs the ovaries can produce.

With egg freezing, an additional factor to consider is the chances of eggs thawing successfully.

Current thinking is that women under 35 should try to freeze 20 eggs and women over 35 20-30 eggs. However, a woman’s ovaries may respond very differently to stimulation, which means multiple egg freeze cycles may be required to achieve this number.

How long can I store my eggs?

Once vitrified, eggs may be stored for any period up to a maximum of 55 years from the date they are first placed in storage. However, you must renew your consent every ten years; therefore, you must keep your contact details updated with us.

What happens when I’m ready to use my frozen eggs?

Your eggs will be transported from the cryostorage facility to the clinic and thawed. They will then be fertilised with partner or donor sperm using a fertility process called ICSI.

What happens next?

If you decide to proceed with egg freezing, the first step is a consultation with one of our fertility experts and a fertility assessment. Once any relevant investigations are completed, your consultant will discuss the results with you and any implications. They will inform you of what to expect from egg freezing and provide a detailed, fully costed treatment plan.

You will then attend a nurse planning appointment. During this appointment, we will map out the timeline of your egg-freezing treatment. They will also go through the consent process, which will be explained in detail, and your nurse will answer any further questions you may have.

When you are ready to start, you call to tell us when your period has started, and from there, the egg freezing cycle takes approximately 14 days.

If we haven’t answered your egg-freezing question, contact us to find out more.

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Can stress impact your fertility?

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April is Stress Awareness Month and although most of us can manage small amounts of stress – which can even help you focus on achieving short-term goals – chronic stress can eventually affect how you cope with daily life. And, the longer stress lasts, it can even become a threat to your health and wellbeing.

Long-term stimulation of the stress response system means we’re overexposed to cortisol and other stress hormones, and this can lead to mental health problems, insomnia, digestive issues, muscle tension, cardiovascular disease, high blood pressure, stroke, and cognitive impairment.

It is not fully understood how stress affects fertility. Some studies have shown adverse effects, while others don’t, and most are only small-scale studies at this stage. We certainly know that the reverse is true and struggling to conceive can be very stressful. One study published in the Fertility and Sterility Journal surveyed 352 women seeking treatment for infertility and found that more than half of them showed signs of depression and three in four showed signs of anxiety.

So, whether your stress is related to your struggles conceiving or other factors, how does it affect your fertility and pregnancy outcomes?

Stress and your fertility

Stress triggers the body’s fight or flight response. In short, this means releasing stress hormones like cortisol which have an immediate physical impact such as increased heart rate, shallow breathing, high blood pressure and stress headaches.

When you are experiencing a prolonged period of extreme stress, the body will shut down any systems that it does not deem necessary for survival. This is why you can experience hair thinning a few months after a very stressful situation – telogen effluvium is a type of hair loss that results from an interruption in the normal hair growth cycle. In terms of your fertility, this can cause delayed or absent ovulation and irregular or missed periods.

In one small-scale study from 2015, women in the high stress group based on perceived stress assessments were found to have lower levels of oestrogen, progesterone and luteinising hormone. They also had higher levels of follicle-stimulating hormone during a particular stage of their cycles which meant an increased chance of anovulation which is when an egg is released from the ovary during your menstrual cycle. Chronic anovulation is a common cause of infertility.

[ext link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315337/]

Another key stress hormone, CRH or corticotrophin-releasing hormone, is present in diseases that cause inflammation. Abnormal levels of CRH can affect the uterine lining and placenta and therefore could adversely affect implantation.

However, not every study has found a link and 2019 investigation found no difference in conception rates in women based on their daily reported perceived stress levels and a 2017 study of women undergoing IVF concluded that perceived stress and high cortisol levels “were not associated with IVF cycle outcomes”.

Managing stress during IVF

At Aria Fertility, we know how important it is to find ways to manage your stress throughout your fertility journey. Our doctors, nurses and embryology team provide comprehensive patient care combined with a wealth of medical experience and expertise, so you know you are in the best possible hands.

In our Support Hub, we have brought together organisations and individuals that offer fertility support, advice and information. Methods for managing stress encompass counselling, acupuncture, reflexology, and nutritional support.

For more advice on managing stress during your fertility journey, call +44 (0) 203 263 6025 to arrange a consultation.

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What is the difference between egg freezing and embryo freezing?

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Since Jennifer Aniston opened up about her own experiences with IVF and expressed her regret that she had not undergone egg freezing earlier, even more women have begun exploring their fertility preservation options.

Women now have the option of freezing their eggs or embryos, but there are critical differences between the treatments that can determine the best choice for them.

The collection stage

Both procedures start with the same basic premise of egg collection. You will self-administer hormone injections, stimulating the ovaries to produce mature eggs over 8 to 12 days. We will monitor your progress during this stage, and your eggs will be collected at the optimal time. This is a minor surgical procedure performed under sedation in the clinic. The collected eggs are then transferred to our laboratory.

To fertilise or not fertilise

This is the crucial difference between the two treatments. Before they are frozen, the eggs can be fertilised in our laboratory using either your partner’s sperm or donor sperm.

This takes place on the same day as the egg collection. Our embryologist will try to fertilise all mature eggs using intracytoplasmic sperm injection, or ICSI. If successful, the fertilised eggs will develop into an embryo. Over the next five to six days, the embryos will be carefully monitored as they hopefully progress to the blastocyst stage. The embryos that successfully develop to this stage are then frozen.

The freezing and storage process

Both eggs and embryos are frozen and stored using a method known as cryopreservation. Water in the cell is replaced with a freezing solution called a cryoprotectant which prevents this water from crystallising in the freezing process. The freezing process is called vitrification and entails flash freezing, instantaneous cooling from 37oC to -196oC. The eggs or embryos are then stored in liquid nitrogen.

Using your embryos or eggs

When you’re ready to use your embryos or eggs, our embryologist will thaw them. An embryo that has successfully thawed can be transferred directly back into the body. Frozen eggs that survive the thawing process will then be injected with a partner or donor’s sperm to fertilise them. The fertilised eggs will then develop into embryos and after five to six days can then be transferred to the womb.

The pros and cons of egg freezing vs freezing embryos

Previously, slow-freezing technology was used to freeze eggs or embryos. The cells were cooled very slowly over a couple of hours to avoid ice crystallisation until they reached the optimal storage temperature. Embryos were thought to survive the freezing and thawing process better than eggs as the latter are large size cells with a high-water content, so they are more susceptible to ice crystals forming and causing cellular damage.

The introduction of vitrification or flash freezing has largely eliminated this difference, and the survival rates when freezing eggs versus embryos are now very similar.

Choosing to freeze embryos means you have more information on how many eggs were healthy enough to fertilise and begin development. However, the most important difference is that freezing eggs rather than embryos grants women reproductive autonomy, giving them more options in the future.

Aria Fertility Counselling

Discussing your treatment choice with one of our counsellors can be a very rewarding and empowering session. At Aria, we wish for everyone undergoing fertility preservation treatment to have a full understanding of choices they are making and implications these may have for the future. Our wonderful counsellors will always be able to spare time to have a chat with you and help you come to a decision if you feel you require their expert support.

If you have more questions about our fertility preservation options, call +44 (0) 203 263 6025 or email admin@ariafertility.co.uk to arrange a consultation with one of our fertility specialists.

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What are mosaic embryos?

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New research has found that mosaic embryos, currently ruled out for IVF selection, could self-correct and lead to healthy pregnancies.

During embryo selection, a test known as preimplantation genetic testing for aneuploidy (PGT-A) is used to screen aneuploid embryos which have an incorrect number of chromosomes. This is performed to reduce the risk of miscarriage.

Embryos with the correct number of chromosomes are called euploid and have a higher chance of leading to a successful pregnancy than those with the incorrect number of chromosomes or aneuploid embryos.

What are mosaic embryos?

Previously, embryos were categorised as normal or abnormal, but in the mid-2010s, embryologists discovered that blastocysts aren’t necessarily 100% euploid or 100% aneuploid: sometimes they’re a mixture.

The term mosaic embryos were coined to describe embryos that have a mix of normal and abnormal cells. Data suggests that mosaic embryos account for up to 20% of all PGT-A-tested embryos.

Mosaic embryos can have different proportions of normal and abnormal cells and there is a criterion ranging from low-level mosaic where 20 to 40% of the cells are abnormal to high-level mosaic.

What did the study into aneuploid embryos find?

Scientists at the laboratory of synthetic embryology at Rockefeller University, New York found that some aneuploid embryos can self-correct. They transferred embryos that had failed the PGT-A screen into women who’d given their consent. Genetic tests performed a few months later found there were no longer any signs of aneuploidy.

The next stage of the study was to understand how the ‘faulty’ embryos developed. Using human embryonic stem cells, they generated artificial human embryos and studied their development. They found that the proportion of the aneuploid cells decreased and the aneuploid cells that remained were in the outer layer which eventually becomes part of the placenta.

As this research shows, the science behind embryo selection continues to evolve and PGT-A is one tool to help us choose which embryos to transfer. Throughout the process, we provide you with all the information you need to make these important decisions.

For more advice on IVF and embryo selection, call +44 (0) 203 263 6025 to arrange a consultation at Aria Fertility.

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Why do I need to freeze so many eggs?

The more eggs you freeze, the higher your chance of success is regarding fertilisation. This is because at each stage of the process there is a decrease in the number of eggs that survive to the next one. Dr Anna Carby outlines each stage and how the number of eggs decreases between them.

“The thaw survival rate for eggs is between 80 and 90%. Of that surviving thaw, the fertilisation rate is approximately 60 to 70%. Of the fertilised eggs remaining approximately 40% may be usable in terms of either transfer or freezing as embryos. It can be seen therefore that starting with 20 eggs may result in three or four embryos being produced.

“You must also be aware that occasionally these percentages are lower when it comes to thawing and that it is possible, though far less likely, that no embryos are produced as a result of thawing.”

What should you look for in a fertility clinic?

Dr Carby clarifies how “the skill of your team will contribute to the potential success of treatment if you use your eggs in the future. Speak to as many clinics as you can before deciding which clinic to go to. This usually gives you a good indication as to the level of service and the feel of the clinic and team.

“Find out if your clinic offers investigations before or during your consultation which can cut down on the visits required to the clinic.”

Contact us with any inquiries that you have regarding the egg freezing treatment by calling us on 0203 263 6025 or emailing us at admin@ariafertility.co.uk.

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What happens after egg freezing?

After egg freezing, there are many different paths that you can take. Dr Anna Carby discusses the different possibilities.

How long can I store my eggs after egg freezing?

After the fertility preservation treatment, your eggs will be stored, however, there is a limit. “Currently eggs can be stored for 10 years. However, in some circumstances, you may be able to store your eggs for up to 55 years.”

Interestingly, though, this limit has been extended in view of COVID-19.

What would I need to do to use my eggs in the future?

“The process of preparing for an embryo transfer is easier than the stimulation and egg collection required for egg collection. Usually, either oestrogen tablets or patches are used to build up the womb lining for approximately two weeks.

“If the lining looks thick enough on the ultrasound scan, progesterone is then used before embryo transfer to synchronise the lining to the age of the embryo generated,” Dr Carby explains. “This usually means starting progesterone on the day eggs is thawed. These medications then need to be continued until 12 weeks of pregnancy after which time they can be stopped.

“Once eggs have been thawed, they are injected with sperm using a process called ICSI (intracytoplasmic sperm injection) as the normal layer of surrounding cells is stripped before freezing to allow rapid colling of the eggs.”

What if I don’t use my eggs?

Egg freezing is often chosen as insurance, but what if you find you don’t need to use those eggs in the future?

As Dr Carby elaborates, “only approximately 10% of women freezing their eggs ever use them. This is because some will get pregnant naturally when they find a partner or others may decide they don’t wish to use them.”

Contact us with any queries that you have regarding the egg freezing treatment by calling us on 0203 263 6025 or emailing us at admin@ariafertility.com.

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GET IN TOUCH.

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OPENING HOURS.

Mon – Fri: 9am – 5pm

CLINIC LOCATION.

8 Welbeck Way  London  W1G 9YL

CONTACT US.

+44 (0) 203 263 6025

admin@ariafertility.co.uk

Fertility Clinic London Location

Authorised by the Human Fertilisation Embryology Authority

LEGAL ARIA PATIENT PORTAL
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