What is the difference between natural IVF and stimulated IVF?

Natural IVF works with your body’s natural cycle and involves little to no fertility medication. Only one egg is collected, making the process gentler. Stimulated IVF uses hormone injections to produce multiple eggs. This can improve the chances of fertilisation, but it also involves more medications.

Is a natural IVF cycle better than stimulated IVF?

It really depends on your situation. Natural IVF might be a better fit if you’re looking for a gentler process with fewer side effects. Stimulated IVF is chosen for higher success rates per cycle.

Natural Cycle IVF vs Stimulated IVF: Key Differences

When you're exploring fertility treatments, it helps to understand the options available. In vitro fertilisation (IVF) is one of the most common methods used to support conception. But even within IVF, there are different approaches. Two terms you might come across are natural cycle IVF and stimulated IVF. Both are ways to help you conceive, but they work quite differently. Knowing these differences can help you choose what feels right for you. Once you know how each method works, it becomes easier to weigh your options.

Understanding Natural Cycle IVF

Natural cycle IVF is a gentle approach that works with your body’s natural menstrual cycle. It focuses on collecting the one egg your body naturally produces each month without using drugs to stimulate your ovaries to make more eggs. The goal is to keep things as natural as possible. This is what a typical natural cycle IVF process might look like:

A single injection (like hCG or Lupron) may be used to trigger egg release. Progesterone is often given after retrieval to support the uterine lining.
Fewer appointments and simpler egg retrieval make it less demanding.
The treatment prioritises the quality of the single egg over quantity.

This method feels closer to natural conception because it avoids heavy hormonal interference. However, timing is critical to catch the egg before ovulation and there’s no backup if the egg isn’t viable.

Understanding Stimulated IVF

Stimulated IVF is the more common approach. It uses fertility drugs to stimulate your ovaries to produce multiple eggs in one cycle. The process usually includes the following steps:

Ovarian stimulation: Drugs like follicle-stimulating hormone (FSH), human chorionic gonadotropin (hCG) and gonadotropin-releasing hormone (GnRH) agonists or antagonists are used to grow multiple egg-containing follicles.
Multiple egg retrieval: Several eggs are collected in one go to increase the chances of viable embryos.
Close monitoring: Regular ultrasounds and blood tests track follicle growth and hormone levels.
Embryo selection: Multiple eggs are fertilised in the lab, allowing the best embryos to be selected for transfer.
Freezing option: Extra embryos can be frozen and stored for use in future cycles

Key Differences Between Natural Cycle IVF and Stimulated IVF

The biggest difference between the two options lies in how they handle egg production and the treatment timeline:

Difference	Natural Cycle IVF	Stimulated IVF
Hormonal stimulation	Relies on your body’s natural hormones with little or no medication.	Involves a 9 to 12 day course of fertility drugs to stimulate multiple follicles.
Egg retrieval	Only one egg is retrieved.	Retrieves multiple eggs through a more complex procedure under sedation.
Monitoring	Fewer clinic visits as it tracks your natural ovulation.	Frequent ultrasounds and blood tests to monitor response and adjust medications.
Embryo creation	Typically results in one embryo.	Produces multiple embryos, giving more options for transfer or freezing.

Success Rates and Outcomes

Success rates are a key factor when choosing between these treatments:

Natural cycle IVF: Success rates are lower, around 7 to 16 per cent per cycle due to relying on a single egg. There’s a higher chance of cycle cancellation if ovulation happens early or the egg isn’t retrieved. It’s lower success rate means you might need multiple cycles, which can add up in cost and emotional strain.
Stimulated IVF: Success rates can be as high as 40 to 45 per cent per cycle for individuals under 35. Retrieving multiple eggs gives you a better chance of getting healthy embryos.

Benefits of Natural Cycle IVF and Stimulated IVF

Both methods have unique advantages that might appeal to you depending on your priorities.
Natural Cycle IVF Benefits:

Lower risk of complications like ovarian hyperstimulation syndrome (OHSS) as no stimulation drugs are used.
Reduced side effects since you avoid heavy medications. This means less bloating, mood swings, or injection-site discomfort.
More affordable per cycle due to minimal drug costs.
Less invasive with fewer appointments and a simpler egg retrieval process.

Stimulated IVF Benefits:

Higher success rates per cycle, increasing your chances of pregnancy sooner.
Option to freeze extra embryos for future cycles.
Allows genetic screening (like PGT-A, PGT-M, or PGT-SR) to select healthy embryos.
Effective for a wider range of fertility issues, such as PCOS, endometriosis, or male factor infertility.

Risks and Limitations
Each approach comes with its own challenges and potential risks:
Natural Cycle IVF Risks:

Higher cancellation risk due to premature ovulation or failure to retrieve an egg.
Lower success rates for individuals over 37 or those with low ovarian reserve.
No extra embryos for future use, meaning you start from scratch if a cycle fails.
Limited suitability for people with irregular ovulation or severe fertility issues.

Stimulated IVF Risks:

Risk of OHSS, though severe cases are rare with careful monitoring.
Side effects from medications, like bloating, mood swings, or injection pain.
Higher cost per cycle due to expensive fertility drugs and more intensive monitoring.
Small risk of multiple pregnancies if more than one embryo is transferred.

Who Are These Treatments Suitable For?

Your fertility profile will guide which option is best for you:
Natural Cycle IVF is Suitable for:

Individuals with regular ovulation and good ovarian reserve, especially those under 35.
Those with low egg reserve, high FSH, or low AMH who want to avoid heavy stimulation.
People with conditions like severe endometriosis or hormone-dependent cancers.
Those who prefer minimal medication.
Patients who’ve had poor responses to stimulated IVF or failed implantations.

Stimulated IVF is Suitable for:

Individuals with a good ovarian reserve who can handle stimulation drugs.
Those with fertility issues like PCOS, endometriosis, or male factor infertility.
Couples wanting to screen embryos for genetic conditions.
Individuals seeking higher success rates or the option to freeze embryos for future use.

Endometrial Receptivity and Hormonal Response

The way these treatments affect your uterine lining (endometrium) and hormones is another key difference:

Natural cycle IVF: Your body’s natural hormones (oestrogen and progesterone) prepare the endometrium, leading to a thicker, more receptive lining. This can improve implantation chances.
Stimulated IVF: Medications control hormone levels, which can result in a thinner endometrium. However, careful monitoring makes sure the lining is ready for embryo transfer.

Choosing between natural cycle IVF and stimulated IVF depends on your unique situation. The right choice comes down to your health and fertility needs. Both options have their advantages, and what works for one person might not work for another. Talk to your doctor about your age, budget, and emotional readiness to decide which path is best for you.

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FAQs on What Is The Difference Between Natural Cycle IVF & Stimulated IVF

What is the difference between natural IVF and stimulated IVF?
Natural IVF works with your body’s natural cycle and involves little to no fertility medication. Only one egg is collected, making the process gentler. Stimulated IVF uses hormone injections to produce multiple eggs. This can improve the chances of fertilisation, but it also involves more medications.
Is a natural IVF cycle better than stimulated IVF?
It really depends on your situation. Natural IVF might be a better fit if you’re looking for a gentler process with fewer side effects. Stimulated IVF is chosen for higher success rates per cycle.