Different IVF Protocols: Stimulation & Fertilization Treatment

Explore different IVF protocols: stimulation & fertilization treatment options. Understand IVF protocol types, stimulation protocols, and which fertility treatment may be right for you.

When starting an IVF treatment, one of the most important decisions is choosing the right stimulation protocol. And yet, many women find this part of the process hard to understand. What’s the difference between a short and a long protocol? Why are there so many variations? And how do these choices affect the number of eggs, the success of fertilisation, or even your wellbeing during treatment?

In this guide, we explain how stimulation protocols work – and why they are such a central step in the IVF process. We’ll walk you through the most commonly used IVF protocols, from the widely known antagonist and long protocols to lesser-known options like mild or microdose flare stimulation. You’ll learn what each approach means for your body, how follicles are monitored, what kind of medication is typically used to stimulate the ovaries, and what your fertility specialist might take into account when recommending one over another.

It’s also important to know that stimulation strategies can differ a lot from one country to another. If you’re considering IVF abroad, the medication protocol used may vary depending on local practice, regulations and even drug availability. In some cases, you might also be able to purchase medication internationally – which can lead to significant cost savings. We’ve seen patients reduce their IVF medication expenses by up to €1,000 per cycle by sourcing prescriptions outside their home country.

This guide doesn’t give medical advice. Instead, it’s here to help you understand what’s happening behind the scenes, so you feel more informed and supported when planning your treatment. Whether this is your first IVF cycle or you’ve had previous IVF experience, this article will help you make sense of the different protocols and how they might impact your fertility journey.

Ready to understand what’s behind the protocol – and how to find the right path for you?

Let’s get started.

What is an IVF protocol and why does it matter?

An IVF protocol is the personalised treatment plan that determines how your body will be prepared for egg retrieval and embryo creation. It defines which medications are used, in what dose, and on which days of your cycle. While the term might sound technical, it’s simply the roadmap that guides each phase of ovarian stimulation and helps your clinic coordinate the timing of every step – from the start of injections to the moment of egg collection.

There is no such thing as a one-size-fits-all protocol. Every woman’s reproductive system responds differently, and your protocol is designed to give your ovaries the best possible chance to produce mature eggs. The goal is to stimulate your ovaries to develop multiple follicles, each containing a potential egg, while also reducing the risk of complications such as premature ovulation or ovarian hyperstimulation syndrome.

Fertility specialists often choose the protocol based on various factors – such as your age, ovarian reserve, previous IVF experience or how you responded to past stimulation. In some cases, the aim is to retrieve as many eggs as possible; in others, the focus might be on quality over quantity.

Understanding the protocol used in your IVF cycle doesn’t mean you need to know every medical detail – but it can help you feel more involved and confident in your treatment. When you understand why certain steps are taken and what they aim to achieve, the process often feels less overwhelming.

Understanding ovarian stimulation in the IVF process

Ovarian stimulation is one of the first and most crucial steps in the IVF process. It refers to the phase in which your ovaries are gently encouraged – through a carefully chosen protocol – to produce more than the usual one egg per menstrual cycle. The aim is not only to retrieve multiple eggs, but also to give you the best chance of developing healthy embryos for fertilisation and transfer later on.

This part of the treatment is highly individual. While one woman may respond well to a low dose, another may need a different protocol entirely. Your ovarian reserve, age and previous IVF experiences often influence how the stimulation protocol is designed. Fertility specialists look at all these factors before deciding which medications and which timeline will be most effective for you.

In essence, ovarian stimulation creates the conditions for the next phases of IVF – egg retrieval, embryo development and ultimately implantation. That’s why understanding how it works can help you follow each step more calmly and feel more in control of your treatment.

How IVF stimulation protocols support follicle development

Once the stimulation phase begins, the ovaries are encouraged to develop multiple follicles – each one a tiny fluid-filled sac that can contain a potential egg. The more mature follicles develop, the more chances you may have to retrieve viable eggs.

Stimulation protocols are designed to balance two important goals: encouraging the ovaries to produce enough follicles, but avoiding an overstimulation that could lead to side effects like ovarian hyperstimulation syndrome. It’s a careful balance between effectiveness and safety – and it’s why the protocol is adjusted so precisely.

The number of follicles you see on ultrasound during stimulation doesn’t always mean that many mature eggs will be retrieved. Some follicles grow faster, some slower – and the hormone doses you receive help guide this development. Your medical team monitors the size of the follicles closely, often adjusting your medication dose to fine-tune your body’s response.

The role of hormones, injection timing and dose adjustment

During this phase, hormone levels and timing are everything. Most protocols use injections containing FSH or a combination of FSH and LH to stimulate the ovaries. The exact dose can change depending on how your body responds during the stimulation phase.

Your clinic will monitor hormone levels in your blood and the size of your follicles via ultrasound. Based on this information, they may increase or lower your dose – or sometimes adjust the timing of your injections. This flexibility is part of what makes IVF protocols so personalised.

What might feel like a routine injection each day is in fact a key part of a finely tuned plan. The goal is to support your follicles’ development so that enough mature eggs are ready for collection – without triggering ovulation too early.

It’s natural to feel unsure about the many details – but know that each adjustment is there to give your body the best possible support.

Monitoring follicles during stimulation IVF

Throughout ovarian stimulation, regular monitoring is essential to track how your body is responding to the medication protocol. This is usually done through transvaginal ultrasounds and blood tests. The ultrasounds allow your doctor to measure the size and number of developing follicles in each ovary, while bloodwork checks your hormone levels – especially estradiol, which rises as follicles grow.

Monitoring isn’t just a routine check – it’s how your clinic decides whether to adjust your dose, continue stimulation for a few more days, or schedule your egg retrieval. If your follicles are not growing as expected, the protocol may need to be adjusted. On the other hand, if your response is too strong, your team will take steps to reduce the risk of ovarian hyperstimulation syndrome (OHSS).

The goal is to retrieve mature eggs – not just many follicles. That’s why timing is everything. Once enough follicles reach the ideal size, a final injection (often hCG or a similar hormone) is given to trigger final egg maturation. Your egg retrieval will then be scheduled about 36 hours later.

For many patients, this phase brings both hope and stress. Knowing what to expect during monitoring can make the experience feel a bit more predictable – and remind you that every scan and blood draw is helping to fine-tune your path toward IVF success.

The short protocol – fast-track stimulation and fertilisation

The short protocol is often seen as a more straightforward and faster approach to IVF stimulation. Unlike longer protocols that involve weeks of preparation, this one starts on day 2 or 3 of your menstrual cycle with immediate stimulation using FSH or a combination of FSH and LH. Within a few days, a GnRH antagonist is introduced to prevent premature ovulation. The goal is to stimulate the ovaries efficiently and move quickly toward egg retrieval and fertilisation.

Because this protocol skips the down-regulation phase, your natural hormone activity isn’t fully suppressed. That means it relies more heavily on your body’s own signals – supported by carefully timed injections. It typically results in a shorter overall timeline and a reduced medication burden, making it appealing for many women.

For some, the short protocol may also lower the risk of overstimulation. However, the number of eggs retrieved can vary, depending on your ovarian reserve and how your body responds. It’s not necessarily better or worse – just a different way to reach the same goal: fertilisation of mature eggs that lead to healthy embryos.

Who responds well to the short protocol?

The short protocol is often recommended for women who are considered poor responders – meaning their ovaries don’t produce a high number of follicles even with higher doses of stimulation. If you’ve had a previous IVF cycle with low egg yield, or your ovarian reserve is diminished, this approach might be more suitable.

It’s also a good option for women with regular menstrual cycles and normal hormone levels, who may not require heavy down-regulation. Because the protocol works more in sync with your body’s natural rhythm, it’s sometimes favoured by fertility specialists aiming for a gentler intervention.

Women with a history of endometriosis, or those preparing for a frozen embryo transfer later on, might also benefit from this shorter, less intensive method. And since it uses fewer medications overall, it can help reduce the risk of ovarian hyperstimulation syndrome, especially in those who are sensitive to fertility drugs.

Ultimately, your doctor will consider your age, hormone profile, and previous response to stimulation before suggesting this path. It’s not about choosing the shortest or easiest way – but about tailoring the protocol to your individual biology.

What to expect during a short stimulation cycle

When starting a short IVF protocol, stimulation typically begins on day 2 or 3 of your menstrual cycle. That’s when you’ll start injecting medication – usually a combination of FSH and LH – to stimulate the ovaries to produce multiple follicles. Unlike longer protocols, there’s no phase of hormonal suppression before this step. The stimulation starts right away.

Daily injections are usually required for about 8 to 12 days. During this time, your clinic will monitor your follicle development closely using ultrasounds and hormone tests. This monitoring helps ensure the dosage is right and allows the medical team to adjust the protocol if needed. Timing is everything here – the goal is to stimulate the ovaries effectively without triggering premature ovulation.

Once the follicles have reached the desired size and number, a final injection – often hCG – is given to mature the eggs. Egg retrieval is scheduled about 36 hours later, followed by fertilisation in the lab. The resulting embryos are either transferred a few days later or frozen for future use, depending on your treatment plan.

The entire cycle moves quickly, which can feel intense. But it also means fewer days of medication and monitoring, which many women appreciate – especially when trying to keep travel time or days off work to a minimum during treatment abroad.

“The IVF journey is not just medical – it’s emotional, financial, and deeply personal. Having the right protocol is important. But having the right support can make all the difference.”
Nathalie Wiederkehr

The long protocol – gradual down-regulation and control

The long protocol is a more traditional approach in IVF treatment, where the goal is to gain full control over your hormonal cycle before ovarian stimulation begins. It starts in the second half of your previous cycle – often around day 21 – with medication that suppresses the body’s natural hormone production. This step is called down-regulation.

During this phase, a GnRH agonist is commonly used to temporarily switch off your natural reproductive hormone signals. By doing so, your body won’t ovulate spontaneously, which gives the clinic complete control over the timing of your cycle. After about 10 to 14 days, when your hormone levels are low enough, stimulation begins – usually with FSH injections to encourage multiple follicles to grow in the ovaries.

Compared to the short protocol, the long version stretches over more days and requires a bit more patience. But for many patients – especially those with regular cycles and a good ovarian reserve – this extra control can result in a more synchronised follicle response and potentially a higher number of mature eggs retrieved.

Throughout the stimulation phase, your progress is monitored closely via ultrasound and bloodwork. Adjustments to the dose may be made along the way. Once the follicles are ready, you’ll receive a trigger shot, followed by the egg retrieval.

This protocol might sound more intense – and it does require more injections and time – but it’s often recommended when a more predictable and even follicular development is needed.

What is down-regulation protocol and how does it work?

Down-regulation is a key feature of the long IVF protocol. It refers to the process of temporarily switching off your body’s natural reproductive hormone signals to gain full medical control over the cycle. This is typically done using a GnRH agonist, which first stimulates – then suppresses – the release of FSH and LH from the pituitary gland.

At first, this medication may cause a short flare of hormone activity, followed by a shutdown of your natural cycle. You might even experience symptoms similar to menopause, like mild headaches or hot flashes, as your estrogen levels drop. But this temporary hormonal rest is exactly what makes the next step – ovarian stimulation – more controlled and targeted.

Once your hormone levels are sufficiently suppressed, stimulation begins with daily injections of FSH. Because your ovaries are now responding only to the medication – not to your own hormonal fluctuations – the doctor can fine-tune the dose to guide how many follicles grow and how evenly they develop.

Down-regulation helps prevent premature ovulation and improves the timing of the egg retrieval. It’s especially useful when a consistent, well-coordinated ovarian response is the goal – such as in fresh embryo transfers or when trying to retrieve as many mature eggs as possible.

Benefits and challenges of the long protocol

The long protocol has long been considered the classic approach in IVF – and for good reasons. One of its biggest advantages is the high level of hormonal control it offers. By first suppressing your natural cycle and then stimulating the ovaries with carefully adjusted doses of FSH, doctors can often achieve a balanced and predictable follicular response. This can increase the chances of retrieving a good number of mature eggs in one cycle, which is especially helpful when planning for fresh embryo transfer or embryo freezing.

Another benefit is the reduced risk of a mistimed ovulation. Because the ovaries are no longer reacting to the body’s own LH surges, it’s easier to plan egg retrieval precisely – and avoid losing eggs too early. This predictability can be particularly reassuring for women who have previously experienced cycle cancellations or inconsistent responses.

However, the long protocol is not for everyone. The down-regulation phase takes time – typically two to three weeks – which makes the total IVF cycle longer. Some women also find this phase challenging, both physically and emotionally, as the temporary hormone suppression can cause side effects like mood swings, headaches or fatigue. In some cases, the ovaries may respond less efficiently than expected, requiring dose adjustments or changes in stimulation.

The long protocol is often used in women with regular cycles and normal ovarian reserve. But for others – like women with diminished ovarian reserve, PCOS, or those who didn’t respond well in a previous IVF cycle – other stimulation protocols might be more effective.

The antagonist protocol – flexibility with fewer risks

This protocol is often recommended for those seeking a more flexible stimulation phase with a lower risk of ovarian hyperstimulation syndrome. Unlike the long protocol, it does not require a full suppression of the cycle before stimulation begins. Instead, stimulation starts early in the menstrual cycle and the antagonist is introduced only once the follicles reach a certain size – typically to prevent premature ovulation.

Understanding GnRH antagonist protocols

GnRH antagonist protocols use medications that immediately block the body’s release of luteinizing hormone. This helps to avoid early ovulation and allows for better control over the development of ovarian follicles. These medications are typically given via injection and are started mid-way through the stimulation cycle, depending on how your ovaries respond.

When the antagonist protocol is recommended

This approach is commonly used in women with polycystic ovary syndrome or those at higher risk of ovarian overstimulation. It’s also often chosen for its shorter treatment time and reduced hormonal load. The protocol may offer more comfort and fewer side effects, making it a suitable option for many first-time IVF patients – especially if a quicker treatment cycle is preferred or the ovarian reserve is limited.

Flare and microdose flare protocols – for specific responders

Flare protocols are specially designed for women who may need an extra hormonal boost to stimulate their ovaries – often those with diminished ovarian reserve or a history of poor response in previous IVF cycles. Rather than suppressing the natural cycle first, this protocol takes advantage of the initial flare of hormone release triggered by a GnRH agonist.

What is the flare protocol and how does it support ovulation?

When a GnRH agonist is given at the start of the cycle, it causes a short-lived surge in FSH and LH – known as the flare effect. This early hormonal rise is used strategically to encourage the ovaries to start producing follicles. Shortly after this initial flare, the agonist begins to suppress further hormone release, allowing the clinic to take over with stimulation injections like FSH or FSH/LH combinations.

The idea is to give the ovaries a head start – especially when their natural response may be low. This is why flare protocols are usually part of a tailored plan for women with fewer eggs or low AMH levels.

Who might benefit from microdose flare stimulation?

The microdose version of the flare protocol uses smaller amounts of the GnRH agonist, combined with higher doses of stimulation medication. This approach reduces the risk of over-suppression while still taking advantage of the early flare effect. It’s often recommended for women with a low ovarian reserve or those who had disappointing results with other protocols.

Both versions of the flare protocol require very close monitoring and fine-tuned adjustments – but they can offer renewed hope to those who didn’t respond well to standard stimulation in the past.

Mild, natural and low dose IVF options

For some women, less can be more. Mild and natural IVF protocols are gaining popularity for their lower medication load, reduced side effects, and more patient-friendly experience. These approaches are typically recommended for women who wish to avoid aggressive stimulation or who may not benefit from high-dose protocols due to age or ovarian reserve.

What is low dose IVF and who is it for?

Low dose IVF – sometimes referred to as minimal stimulation IVF – involves fewer medications and lower doses of gonadotropins. The goal is not to produce as many eggs as possible, but rather to aim for quality over quantity. This protocol may be ideal for women with diminished ovarian reserve, or for those who prefer a gentler approach with fewer injections and reduced risk of ovarian hyperstimulation.

It can also be suitable for women with medical conditions that make high stimulation unsafe, or for those preparing for egg or embryo freezing who want to repeat cycles multiple times. In some cases, cost can also be a factor – since fewer medications are needed, the treatment may be more affordable.

IVF Naturelle and natural cycle fertilization

Natural cycle IVF takes this concept one step further by avoiding stimulation medication altogether. Instead, the clinic tracks your natural ovulation and retrieves the single egg your body produces on its own. While this approach isn’t for everyone – especially if you need multiple embryos or want to bank eggs – it may be suitable for younger women with regular cycles and strong ovarian response.

Natural IVF can also be used in combination with frozen embryo transfer strategies or as a backup plan when stimulation is not well tolerated. While success rates per cycle are lower, the overall process is less invasive and often more aligned with the body’s rhythm.

Choosing the right IVF protocol for your treatment cycle

No single IVF protocol works for everyone – and that’s exactly why clinics offer different stimulation strategies. The protocol used in your case will depend on a careful evaluation of your medical history, hormone levels, ovarian reserve, and any previous IVF treatments.

Individual factors your doctor will consider

Fertility specialists take many factors into account when choosing the best stimulation plan. These include your age, AMH levels, antral follicle count, past responses to medication, and any underlying conditions like PCOS or diminished ovarian reserve. Your fertility journey is unique, and the protocol should reflect that – whether it involves higher doses, antagonist medications, or a gentler natural approach.

Why protocols differ from clinic to clinic

Protocols also vary depending on the clinic’s experience, lab quality, and local regulations. Some clinics prefer shorter treatment cycles for convenience and cost-effectiveness, while others focus on maximising embryo yield for genetic testing or freezing. There is no universal “best protocol” – what matters most is finding the one that fits your body and your goals.

If you’ve already had treatment and were disappointed by a poor response or too few mature eggs, it might be time to explore a different protocol – or even a different clinic.

Your next step – understanding your options abroad

If you’re starting IVF for the first time, or you’ve already gone through one or more cycles, you may be wondering if another country could offer better options – especially when it comes to protocols that are personalised, flexible, and affordable.

Many women explore IVF abroad not just for legal access to treatments like egg donation or embryo adoption, but also because protocols vary significantly across clinics and countries. Some clinics abroad offer advanced stimulation strategies or are more willing to adjust protocols for low responders, PCOS, or specific medical needs. Others have extensive experience with natural and low-dose IVF, and some even combine different protocols across multiple cycles to improve egg yield and embryo quality.

At the same time, medication costs can be significantly lower in some countries – not just because of local prices, but also due to partnerships with pharmacies. If you know where to look, it’s possible to save over €1,000 per IVF cycle on medications alone. And yes – I know where.

You don’t have to figure it out alone.

Download my free guide and discover what’s possible in Europe – clearly, honestly, and without the overwhelm.