USING: IVF With Frozen Eggs
What actually happens between thawing your eggs and (hopefully) holding a baby
Egg freezing is sometimes spoken about as if it were a single decision: “I froze my eggs.” When you decide to use them it the start of another chapter, the second half of the journey, IVF with its own steps, decisions, and uncertainties.
If you're at the point of thinking about using your frozen eggs, this guide walks you through what actually happens, in plain English. From the lab thawing your eggs to (hopefully) embryo transfer and beyond, we'll explain each stage, what shapes the outcomes, and the realistic timelines.
The honest headline: using frozen eggs still involves multiple stages, each with its own outcomes. Egg freezing has become more successful but is by no means a guarantee of having a baby. Knowing what to expect at every step helps you plan, prepare, and protect yourself emotionally.
Where IVF with frozen eggs fits in the bigger picture
IVF stands for in vitro fertilisation, fertilising an egg with sperm in the lab rather than the body. When you use frozen eggs, the procedure is essentially the same as a fresh IVF cycle from the moment of fertilisation onwards, with one big difference: instead of producing eggs through a brand new stimulation cycle, you're using ones you already have in storage.
That means you can usually skip the heavy hormone stimulation stage and the egg retrieval procedure. But everything that comes after (fertilisation, embryo development, transfer, and the wait) is the same as any other IVF cycle.
Step 1: Pre-treatment and your IVF workup
Before your eggs are thawed, if you plan to carry your pregnancy yourself, your clinic will run a fresh round of checks. Even if your fertility was assessed when you originally froze, things can change over the years between freezing and thawing.
You'll typically need:
An ultrasound scan of your uterus and ovaries.
Blood tests including hormone levels and viral screening (Hepatitis B, Hepatitis C, HIV and HTLV).
Updated consent forms for the use of your eggs.
A discussion of which sperm you'll use — your partner's, a donor's, or a previously frozen sample.
UK law requires written consent before any fertility treatment can begin, including specifying who any embryos created can be used by and for how long they can be stored.
Step 2: Preparing your body for embryo transfer
If you're going to receive an embryo back, your uterus needs to be ready. There are two main approaches:
Natural cycle
If you ovulate regularly, your clinic may track your natural cycle and time the embryo transfer around your own ovulation. This involves fewer drugs but more frequent monitoring scans.
Medicated cycle
Most women using frozen eggs have a medicated cycle. You'll take oestrogen (usually as tablets, patches, or pessaries) for around two to three weeks to thicken the lining of your uterus, then add progesterone in the lead-up to embryo transfer. Your clinic will choose between these depending on your cycle, your medical history, and clinic preference.
This stage typically takes around three to six weeks from your first medication.
Step 3: The thaw
On the day, the embryology team warms your eggs in a carefully controlled lab process. Vitrified eggs (the standard UK technique) are brought from minus 196°C up to body temperature in minutes, with the cryoprotectants gradually washed out.
Some eggs survive intact; others don't. You can read more about this in our “Guide to Egg Thawing”. Only the eggs that survive move on to fertilisation. We have a separate guide on egg thawing if you want more detail on this stage.
Step 4: Fertilisation
With frozen eggs, fertilisation is almost always done with ICSI (intracytoplasmic sperm injection) a technique where a single sperm is injected directly into each surviving egg under the microscope.
Why ICSI rather than standard IVF? Because the freezing process can change the outer layer of the egg in subtle ways, making natural fertilisation less reliable. The HFEA and most UK clinics treat ICSI as the default with frozen eggs to give each one the best chance.
Not every fertilised egg will go on to develop. In the Guy's Hospital UK study, the average fertilisation rate after ICSI was around 67%. So if 10 of your thawed eggs survived, around 6 or 7 might be successfully fertilised.
Step 5: Embryo development
Over the next five to six days, the fertilised eggs are kept in a special incubator and watched closely. Embryologists check progress at set points to see which embryos are dividing well and which have stopped.
This is normal. Not every fertilised egg becomes a healthy embryo, and the drop-off mostly reflects the egg's chromosomal health at the time it was originally frozen. It is rarely something you can change.
Most UK clinics aim for a blastocyst transfer, which means transferring an embryo at day 5 or 6 of development, when it has reached around 100 cells. Blastocyst-stage embryos generally have higher implantation rates than earlier-stage ones, although not every fertilised egg will reach this stage.
Step 6: Embryo transfer
The transfer itself is short and most women find it less invasive than the egg retrieval. A thin catheter is used to place the embryo into the uterus, guided by ultrasound.
UK clinics generally transfer one embryo at a time. The HFEA actively promotes single embryo transfer to reduce the risk of multiple pregnancy, which carries higher health risks for both mother and babies. If you have multiple good embryos, the additional ones can be frozen for future transfers, known as a frozen embryo transfer (FET) cycle.
Step 7: The two-week wait
After the embryo transfer, there's a wait of around 9 to 14 days before a pregnancy test. Your clinic will tell you exactly when to test, and how. You'll continue progesterone (and possibly oestrogen) during this time to support a potential early pregnancy.
This is often the hardest stage emotionally. You may feel anxious, hopeful, fearful, or numb, sometimes all in the same hour. None of these reactions is unusual. Many people find it helps to plan light distractions, ask for time off work if possible, and avoid 'symptom-spotting' on Google/ Chat GPT.
Fresh vs frozen embryo transfer: what's the difference?
With frozen eggs, you'll often hear two terms that can be confusing:
Fresh embryo transfer
This is when the embryo created from your thawed eggs is transferred to your uterus a few days later, in the same cycle. Your eggs were frozen, but the embryo itself was not.
Frozen embryo transfer (FET)
This is when an embryo is created, then frozen, and transferred in a later cycle. This can happen if you have multiple embryos, your clinic recommends a delay (for example, to optimise your hormone levels), or you want to keep some in storage for a future child.
According to the HFEA, the proportion of frozen embryo transfers in UK IVF has been rising for years and now accounts for roughly half of all embryo transfer cycles.
Both routes are well established. Your clinic will recommend the right one for your situation.
How long does the whole process take?
From your initial consultation to a pregnancy test, you should plan for around 8 to 12 weeks. Here's a rough breakdown of what to expect:
Timeline
Stage
Weeks 1–3
Initial consultation, fertility checks, blood tests, scans, viral screening, signing consent forms, counselling appointment.
Weeks 3–6
Hormonal preparation of the uterus (oestrogen, then progesterone) in a medicated cycle, or monitoring of a natural cycle.
Day of thaw
Eggs are warmed and assessed. Surviving eggs are fertilised with ICSI on the same day.
Days 1–6 after thaw
Embryo development is monitored in the lab. Most UK clinics aim for a day 5 or 6 blastocyst transfer.
Day 5 or 6
Embryo transfer: a short, gentle procedure to place one embryo in the uterus.
9–14 days later
Pregnancy test. If positive, an early pregnancy scan is usually scheduled around 7 weeks.
If you're going through a frozen embryo transfer (FET) cycle rather than a fresh transfer, add an extra few weeks for the embryo creation, freezing, and the next cycle's lining preparation.
Success rates and what shapes them
Here are the things that most influence whether a frozen-egg IVF cycle leads to a baby:
Your age when your eggs were frozen
Your age at freezing has a much greater effect on success than your age at thawing. The Nuffield Council on Bioethics has reported that live birth rates are typically around 50% for women who froze eggs under 35, and around 23% for those who froze at 36 or older.
How many eggs you froze
More eggs means more chances at every step. Researchers in the Journal of Human Reproduction estimate that freezing 20 eggs at age 34 may give around a 90% chance of at least one baby; freezing 20 eggs at 37 drops this to around 75%; and at 42, it drops to around 37%. UK research suggests freezing 15 or more eggs is encouraging across age groups.
The clinic's experience
Outcomes vary between clinics. The HFEA Choose a fertility clinic tool publishes the success rates for every UK clinic, broken down by age and treatment type. It's the single best place to compare clinics objectively.
Sperm quality
Even with ICSI, sperm quality matters. If you're using a partner's sperm, a fresh semen analysis at the start of treatment is standard practice. If you're using a donor, donor sperm in the UK has been thoroughly screened.
Your overall health and uterine environment
Conditions such as fibroids, endometrial polyps, or untreated thyroid problems can affect implantation, regardless of egg quality. This is why clinics check your uterus and bloods carefully before transfer.
What the UK numbers actually look like
The HFEA's most recent reports show:
Egg freezing cycles in the UK rose from 2,567 in 2019 to 6,932 in 2023 — a 170% increase.
Despite this growth, the number of patients returning to use stored eggs remains low.
In the Guy's Hospital UK cohort, the pregnancy rate per embryo transfer was around 48% and the live birth rate per embryo transfer was around 35%.
HFEA data shows the birth rate per cycle from frozen donor eggs is around 30%, compared to 18% for women using their own thawed eggs.
That last point is important. Donor eggs come from younger women, and so success rates from donor eggs are higher. If a clinic quotes a single “average” success rate, ask whether donor cycles are mixed in.
Practical takeaways: what should you do next?
Have a pre-IVF consultation with the clinic that holds your eggs. Ask for a written treatment plan, including all costs.
Compare clinics on the HFEA website if you have any flexibility about where to be treated you may want to consider moving your eggs from the clinic you froze in to another clinic.
Ask about ICSI by default: Confirm it's included in the price quoted, since with frozen eggs it usually is.
Plan for time off: Schedule scans, the transfer day, and the two-week wait into your calendar early.
Line up emotional support: A partner, friend, fertility counsellor, or Egg Therapist. The two-week wait is often harder than the medical bits.
Clarify what happens to additional embryos: If you create more than one viable embryo, decide in advance whether to freeze them for later use, donate to research, or discard.
Take the next step with us
At Egg Advisor we help you make sense of the journey from frozen eggs to (hopefully) a baby — independently, without selling treatment, and without taking referral fees. We're here to help you understand your numbers, ask the right questions, and protect your wellbeing throughout.
Use an egg freezing calculator to model your scenarios and chances.
Book a one-to-one appointment with an Egg Advisor for tailored guidance.
Speak to an Egg Therapist for emotional support before, during, or after treatment.
A note from Egg Advisor
Egg Advisor is independent. We share recommendations based on experience, current knowledge and professional practice, and we are not accountable for service provision from other providers. This article reflects UK data and regulation at the time of writing. If your situation changes, please consider booking an appointment with an Egg Advisor for personalised guidance.