Table of Contents
If you have just received your medication protocol before embryo transfer, you are probably staring at a list of drug names you have never heard of and wondering what each one actually does. That is completely normal. Most patients who come to us have the same reaction – a mix of hope, anxiety, and a lot of questions.
This guide walks you through every stage of endometrial preparation exactly as we explain it to our own patients at Beta Plus Surrogacy. No unnecessary medical jargon, no skipping the details that actually matter. By the time you finish reading, you will know what you are taking, why you are taking it, and what to expect at each step.
What Is Endometrial Preparation and Why Does It Matter?
The endometrium is the inner lining of your uterus – the tissue where an embryo implants and begins to grow. For a successful transfer, that lining needs to reach a specific thickness (typically 7–10 mm or more) and a particular texture that embryologists describe as trilaminar, meaning it shows three distinct layers on an ultrasound scan.
When your body is not producing these conditions naturally – as happens in egg donation cycles, frozen embryo transfers, and gestational surrogacy protocols – medication is used to create them artificially. The process usually takes between 10 and 21 days, with 14 days being the most common timeframe in our clinic.
The goal is simple: give the embryo the best possible environment to implant. The four-step protocol below is how we achieve that.
Step 1 – The Training Cycle: Estrogen & Progesterone
The first thing we ask you to do is take one preparatory cycle of estradiol and progesterone before your actual embryo transfer cycle. We call this the training cycle, and its purpose is straightforward: it teaches your body to build and shed the endometrium in a way that we can control and time precisely.
This is also why it does not matter whether you still have your own menstrual cycle or not. The medication replaces that function entirely. Your uterus responds to the hormones regardless of what your ovaries are doing.
Medications used in Step 1:
- Natural estrogen tablets: Progynova, Progynon, Estradiol, Estrofem, Femanest
- Synthetic estrogen + progesterone tablets: Neovletta, Femoden, Marvelon
Step 2 – Down-Regulation: Switching Off Premature Ovulation
At this stage, you will receive a single injection of a down-regulating hormone. The term sounds more alarming than it is. What it does is temporarily pause your ovarian activity for one cycle, which prevents premature ovulation from occurring.
Why does premature ovulation matter? Because if you ovulate early, your implantation window shifts. That window is the short period when the endometrium is at its most receptive to an embryo. If it moves, the transfer date no longer aligns with it — and implantation rates drop significantly.
A note for patients who had a difficult experience with down-regulation in previous IVF cycles:
We hear this regularly. Some patients describe the down-regulation injection in standard long-protocol IVF as causing several weeks of mood changes, fatigue, and brain fog – sometimes severe enough to interrupt daily life. They are understandably reluctant to go through that again.
In an egg donation or embryo transfer cycle, the experience is genuinely different. There are two reasons for this. First, you will already be on estrogen and progesterone from Step 1 before the injection is given – these hormones counterbalance the worst effects of down-regulation. Second, in long-protocol IVF, the artificial menopause phase can stretch to three weeks. In a donor or frozen embryo cycle, it lasts no more than seven days. Most patients in our programme do not report any significant symptoms during that short window.
Refusing down-regulation is possible, but we do not recommend it. Without it, there is a real risk of progesterone rising early and shifting the implantation window, which makes it impossible to proceed with the transfer on schedule. Most patients, once they understand the difference from their previous experience, decide to continue with it.
Medications used in Step 2: Procrene Depot (3.75 mg — single injection), or alternatives: Diphereline Depot, Buserelin Depot, Zoladex, Decapeptyl Depot, or another GnRH agonist as indicated by your clinician.
Step 3 – Estrogen Phase: Building the Lining
Step 3 begins when your previous training cycle ends and menstruation starts. At this point, we will ask you to have your first ultrasound scan with your local doctor. The scan checks two things: the current thickness of your endometrium, and whether any ovarian cysts have developed that might complicate the cycle.
Once we have the green light from that scan, you begin estrogen supplementation – tablets, cream, patches, or a combination of these. Estrogen is the hormone responsible for growing the uterine lining. We use both oral and transdermal (patch) forms because each one behaves slightly differently in the body, and combining them helps maintain more stable hormone levels throughout the day.
After a few days of estrogen, you will have a second scan to measure the lining again. If it is not yet thick enough, we may adjust your dose. This monitoring step is one of the things that distinguishes a well-managed protocol from a generic one — we are not guessing at timing, we are watching the lining grow and responding to what we see.
Estrogen also continues after the transfer itself, sustaining the lining until the embryo’s own placenta is developed enough to take over hormonal support. Stopping it too early is one of the most preventable causes of early miscarriage in donor cycles.
On estrogen doses: Patients sometimes ask whether the amount prescribed is too high. The short answer is that the doses used in endometrial preparation protocols are considerably lower than the estrogen your own placenta will produce in the second and third trimesters of pregnancy. The external medication is not creating anything unusual — it is simply replicating what a natural cycle would do, under controlled conditions.
Medications used in Step 3:
- Estrogen tablets: Progynova, Progynon, Estrodiol
- Estrogen patches: Climara, Estradot, Evorel, Vivelle
Step 4 – Progesterone: The Final Step Before Transfer
Six days before the planned transfer date, progesterone is added to your protocol. This is a critical step. Progesterone shifts the endometrium from a growing phase into a receptive phase — it is the signal that tells the lining it is time to accept an embryo rather than continue developing.
We use two forms of progesterone simultaneously: vaginal pessaries (or cream) and injections. The reason for combining them is evidence-based. Clinical research consistently shows that using both routes together produces better implantation and lower early miscarriage rates in donor and frozen embryo cycles compared to using either alone. The vaginal route delivers progesterone directly to the uterus with minimal systemic effects; the injection ensures consistent blood levels throughout the day.
Progesterone continues after a positive pregnancy test and is maintained until the placenta is capable of producing it independently – typically around weeks 10 to 12 of pregnancy.
Medications used in Step 4:
- Vaginal progesterone: Crinone vaginal gel, Utrogest vaginal pessaries
- Injectable progesterone: Oil-based intramuscular injection as prescribed
Additional Medications: What Else Might Be Included?
Beyond the four core steps, individual patients may be prescribed additional medications depending on their medical history. These typically fall into two categories.
Uterine blood flow support: Certain vitamins and medications improve circulation to the uterus, which supports lining development and embryo implantation – particularly in patients with a history of thin lining or previous implantation failure.
Immunological support: In some cases, especially where there is a history of recurrent pregnancy loss or suspected immune-related implantation issues, low-dose immune-modulating medication may be added to reduce the uterus’s response to the embryo as a foreign body.
Neither of these additions is routine – they are added only when a patient’s specific history indicates they may be beneficial. At Beta Plus Surrogacy, we review each patient’s full medical background before finalising the protocol.
Frequently Asked Questions
How long does endometrial preparation take before embryo transfer? In most cases, the full protocol from the start of the training cycle to the transfer date takes between 10 and 21 days. The most common duration in our clinic is 14 days. The exact timeline depends on how quickly your lining responds to estrogen stimulation.
Can I do endometrial preparation if I no longer have a menstrual cycle? Yes. The medication protocol works independently of your natural cycle. The hormones in Steps 1 and 3 replace the function of your ovaries for the purposes of the treatment. Patients who are post-menopausal, have had an oophorectomy, or have irregular cycles all follow the same protocol.
What is the target endometrial thickness before embryo transfer? Most clinics, including ours, look for a minimum thickness of 7 mm, with the ideal range being between 8 and 12 mm. We also assess the pattern of the lining on ultrasound — the trilaminar appearance is a strong indicator of receptivity, even more so than thickness alone.
Is the down-regulation injection the same as what is used in a full IVF stimulation cycle? The medication is similar, but the experience is usually much milder in a donor or frozen embryo cycle. In standard IVF, the down-regulation phase can last up to three weeks. In a donor cycle, it lasts no more than seven days, and it is preceded by estrogen and progesterone that reduce the side effects. Most patients find it significantly less disruptive than they expected.
Do I need progesterone injections, or can I use the vaginal gel only? For egg donation and frozen embryo transfer cycles, the evidence strongly supports using both forms together. The combination has been shown to produce better outcomes than vaginal progesterone alone. Our team is always available to discuss technique and make the process as manageable as possible.
How long do I continue taking progesterone after a positive pregnancy test? In most cases, progesterone support continues until weeks 10 to 12 of pregnancy, when the placenta takes over hormone production. Stopping earlier than your clinician advises carries a risk of early miscarriage.
What happens if my lining does not reach the required thickness? If the lining is not responding adequately, we adjust the protocol – increasing the dose, changing the form of administration, or extending the preparation phase. In rare cases where the lining consistently fails to develop, we discuss alternative options with the patient individually.
Have more questions about your protocol? Book a free consultation with our team → betaplussurrogacy.com/consultation-application/
