Natural Cycle IVF: Procedure, Benefits, Success Rates, Risks, and Who It's For

What Is Natural Cycle IVF?

Natural cycle IVF or natural IVF, is a version of standard IVF that does not override your body's own monthly cycle with medication.

In a typical menstrual cycle, your ovaries mature and release one egg. Natural cycle IVF retrieves that one naturally selected egg. The egg is fertilised in the laboratory, and the embryo is transferred to your uterus. No injections are used to stimulate the ovaries to produce extra eggs.

The process is closely monitored, but it is gentler on the body than conventional IVF.

In conventional IVF, fertility medications called gonadotrophins (hormones that prompt the ovaries to produce multiple eggs) are injected over several days. The goal is to retrieve several eggs at once, giving more embryos to work with.

Natural cycle IVF skips the stimulation phase entirely. Only the one egg your body chooses naturally is retrieved. Apart from less medication, this means fewer side effects and a simpler process overall. However, the chances per cycle are also reduced.

How Does Natural Cycle IVF Work?

The treatment follows your natural menstrual cycle from start to finish. Here is what each stage involves.

Cycle Monitoring

Monitoring usually begins around day 7 or 8 of your menstrual period. Blood tests measure oestrogen (the hormone that rises as your egg matures) and LH (luteinising hormone that triggers the egg's release from the ovary).

Tracking Follicle Development

Ultrasound scans track the follicle, a small, fluid-filled sac in your ovary that contains the developing egg. Your doctor checks its growth pattern and determines when the egg inside it is ready.

Egg Retrieval

When the follicle reaches the right size, a minor procedure retrieves the egg. It is done under mild sedation or local anaesthesia using a fine needle guided by ultrasound. The procedure takes roughly 20 minutes, and most people go home the same day.

Fertilisation

The egg is placed with prepared sperm in the laboratory. If the sperm count is low or sperm movement is poor, ICSI (intracytoplasmic sperm injection) may be used. It is a technique involving the injection of a single sperm directly into the egg.

Embryo Culture

After fertilisation, the egg develops into an embryo. Embryologists monitor it over the next three to five days.

Embryo Transfer

If the embryo develops well, it is transferred to your uterus through a thin, flexible tube inserted via the cervix or the opening of the uterus. The procedure is generally quick and does not require anaesthesia.

Pregnancy Test

Around 10 to 14 days after the transfer, a blood test checks for hCG (human chorionic gonadotropin), the hormone the body produces after pregnancy begins. A positive result means the embryo has implanted or attached to the lining of the uterus.

Who Is the Right Candidate for Natural Cycle IVF?

Natural cycle IVF may be recommended if you:

• Have regular menstrual cycles and ovulate each month naturally
• Cannot use fertility medications due to a health condition such as a hormone-sensitive cancer
• Have had a poor response to ovarian stimulation in previous IVF, meaning your ovaries produced very few eggs despite medication
• Prefer to minimise medication for personal or medical reasons
• Have a normal ovarian reserve, meaning your egg supply is adequate for your age

Your doctor will assess your full picture before recommending this path.

What Are the Benefits of Natural Cycle IVF?

Natural IVF benefits are most significant for people who are sensitive to medication, have had poor responses to stimulation, or just want a lower-intervention process.

Fewer Fertility Medications

No hormone injections are required in natural cycle IVF. The process is considerably less demanding physically and emotionally for most people.

Lower Risk of Ovarian Hyperstimulation Syndrome (OHSS)

OHSS is a condition where the ovaries swell and become painful in response to fertility drugs. In severe cases, it causes fluid to collect in the abdomen and chest. According to NHS data, moderate to severe OHSS affects approximately 1 in 100 women undergoing stimulated IVF cycles. Natural IVF virtually eliminates this risk because no stimulation drugs are used.

Reduced Medication Side Effects

Fertility drugs used in conventional IVF can cause bloating, mood changes, headaches, and abdominal discomfort. These are largely avoided in natural cycle IVF.

More Natural Hormonal Environment

The uterine lining (the endometrium, the inner layer of the uterus where the embryo implants) develops in response to the body's own hormones. This is considered by some fertility specialists to be a supportive environment for implantation, though research in this area is ongoing.

Shorter Recovery After Egg Retrieval

Only one follicle is punctured during retrieval. Recovery is generally faster than after a conventional retrieval where multiple follicles are involved.

Lower Medication Costs

Fertility medications account for a significant portion of conventional IVF costs. Natural cycle IVF reduces or eliminates this expense.

What Are the Limitations of Natural Cycle IVF?

Similar to most procedures, natural IVF also has a few disadvantages, which are as follows:

Only One Egg Can Be Extracted

This implies only one attempt for that cycle since there will be no further eggs left in case the egg fails to fertilize or develop into an embryo.

High Risk of Cycle Cancellation

It is possible that the egg could be released even before it could be retrieved from the body. The follicle might also fail to grow properly, or the embryo could not develop into a quality embryo. All of these could end up in a cancelled cycle without transfer.

Fewer Embryos Produced

There would not be many embryos produced that could be used for freezing. Conventional IVF tends to produce several embryos, thus offering couples several chances through the same retrieval.

Multiple Natural Cycles May Be Required

It may require several natural cycles before a pregnancy is successful.

May Not Be Suitable for Certain Fertility Problems

It is important to note that natural IVF is not suited for all fertility problems. If you have irregular cycles, do not ovulate reliably, have a very low ovarian reserve, or if your situation requires more intensive intervention, natural IVF may not be the best option

Natural Cycle IVF vs Conventional IVF

The table below shows how natural IVF compares with conventional IVF:

What Are the Success Rates of Natural Cycle IVF?

Natural IVF success rates per cycle are lower compared to conventional IVF, and it is important to understand this reality from the outset.

According to a review published in Human Reproduction Update by Pelinck et al. (2002), live birth rates per started natural cycle IVF range from approximately 7% to 16%, depending on age and individual fertility factors.

However, the Human Fertilisation and Embryology Authority (HFEA) reports that conventional IVF live birth rates per embryo transfer are approximately 38% for women under 35, declining significantly with age.

This gap per cycle does not mean that natural cycle IVF is ineffective. For women who do not respond well to stimulation, adding more medication produces very few additional eggs anyway. In that case, natural IVF success rates can be comparable to what conventional IVF achieves. Cumulative success across several natural cycles can also be meaningful.

Age and egg quality are the strongest predictors of success in any form of IVF.

Are There Any Risks in Natural Cycle IVF?

Natural IVF poses less risk than conventional IVF; however, it is not free of any:

• There is always a chance of infection or slight bleeding, like in any procedure that involves a needle insertion.
• Premature ovulation can occur before egg collection (egg release before egg retrieval).
• Without stimulation, there is a possibility of a greater percentage of cycle cancellations as compared to conventional IVF cycles.
• Unsuccessful repeated cycles can lead to emotional distress. It is a legitimate factor to consider, especially considering that you get one egg per cycle.
• Your physician will analyse your particular risk factors prior to the treatment.

How Can You Prepare for Natural Cycle IVF?

Natural cycle IVF does not have a specific regimen before treatment, but preparation is crucial:

• Attend all scheduled appointments for monitoring. Natural cycle treatment is very timing-sensitive, and missing an ultrasound or blood test could hinder the process of the cycle.
• Stick to a proper sleeping schedule and healthy eating during the weeks preceding your treatment.
• Abstain from smoking and drinking since both will have an impact on your eggs.
• Inform your doctor about any drugs or supplements you use before starting the treatment.
• Be honest with your doctor about the results of any other IVF treatments you've undergone previously.

When Is Conventional IVF a Better Option?

Conventional IVF may be suggested in cases when:

• You have a low ovarian reserve and extracting the highest possible number of eggs from the ovaries is a top priority.
• Your menstrual cycles are unpredictable, or you don’t ovulate properly.
• Several natural cycles of IVF failed to achieve pregnancy.
• The reason for your infertility, including blocked fallopian tubes or severe endometriosis (a condition when tissue that resembles uterine lining grows outside the womb), calls for a more serious procedure.
• You need to undergo preimplantation genetic testing (PGT), which involves screening embryos for genetic conditions and requires multiple embryos to be available.

Conclusion

Natural cycle IVF is a clinically proven treatment that has its distinct role in fertility care. It is neither a compromise nor a secondary choice, but an alternative that can work in certain cases.

In some cases, less medication and a milder procedure are what you need. In other cases, the clinical scenario requires a more aggressive protocol like conventional IVF. What will work to your advantage is correct information and a physician who is aware of your personal case.