How Does Natural Cycle IVF Work?
Quick Answer
Natural cycle IVF follows your body’s own menstrual cycle to retrieve the single egg it naturally produces, fertilize it in a laboratory, and transfer the resulting embryo to the uterus. Unlike conventional IVF, it uses little to no fertility medication, eliminating the risk of ovarian hyperstimulation and significantly reducing costs.
Markham Fertility Centre offers personalized IVF protocols, including natural and modified natural cycles, across five Ontario locations.
How Natural Cycle IVF Differs from Conventional IVF
In conventional IVF, injectable hormones stimulate the ovaries to produce 10 to 15 eggs in a single cycle. Natural cycle IVF skips this step entirely and works with the one egg your body selects on its own.
| Factor | Natural cycle IVF | Conventional IVF |
| Ovarian stimulation | None or minimal | High-dose injectable hormones for 8 to 12 days |
| Number of eggs retrieved | 1 (sometimes 0) | 10 to 15 on average depending on ovarian reserve |
| Daily injections | None (or trigger shot only) | Daily for 8 to 12 days |
| Risk of OHSS | Zero | Low to moderate |
| Clinic monitoring visits | 2 to 3 | 5 to 7 |
| Embryos available for freezing | Rarely unless planning to freeze a single embryo | Often multiple |
| Genetic testing (PGT) | Typically not possible | Available |
| Cost per cycle | Significantly lower | $10,000 to $20,000+ |
| Success rate per cycle (under 35) | 7 to 15% | 40 to 50%, depending on the age of the egg producer |
The core lab procedures (egg retrieval, fertilization, embryo culture, transfer) are identical in both approaches. The difference is entirely in how many eggs are produced and whether medications are used to stimulate the ovaries.
Step-by-Step Process
Step 1: Cycle Monitoring
Starting around day 7 to 9 of your menstrual cycle, your physician tracks the development of your naturally growing follicle through:
- Transvaginal ultrasound: Measures follicle size and uterine lining thickness
- Blood work: Monitors estradiol, LH, and progesterone levels
You will typically visit the clinic 2 to 3 times during this phase. Since only one follicle develops, monitoring is lighter than in conventional IVF.
Step 2: Trigger Shot (Optional)
When the follicle reaches approximately 18 to 20 mm, your physician may administer a trigger injection (hCG) to time the egg’s release precisely. Egg retrieval is then scheduled 34 to 36 hours later.
In some true natural cycles, no trigger is used and retrieval is timed based on the natural LH surge detected through blood work.
Step 3: Egg Retrieval
The retrieval procedure is the same as in conventional IVF:
- Performed using an ultrasound-guided needle through the vaginal wall
- Takes approximately 5 to 10 minutes
- Can be done under light sedation or local anesthesia (no general anesthesia required)
Because only one follicle is targeted, the procedure is shorter and recovery is faster. At Markham Fertility Centre, an anesthesiologist is present at every egg retrieval to ensure a pain-free experience.
Important: Not every follicle contains a retrievable egg. It is possible that no egg is retrieved, which would result in cycle cancellation.
Step 4: Fertilization and Embryo Culture
The retrieved egg is fertilized with partner or donor sperm in the laboratory using conventional insemination or ICSI. The embryo is monitored for 3 to 5 days as it develops.
Since there is typically only one embryo, there are no spare embryos to freeze or test genetically (PGT).
Step 5: Embryo Transfer
If the embryo develops normally, it is transferred to the uterus via a thin catheter. The procedure takes a few minutes and requires no sedation. A pregnancy blood test is typically performed 10 to 14 days later.
Modified Natural Cycle IVF
A variation called modified natural cycle IVF uses minimal medication to improve timing and reduce the risk of premature ovulation:
- A GnRH antagonist may be given to prevent the egg from releasing too early
- A trigger shot (hCG) is used to precisely time retrieval
- Low-dose oral medications (letrozole or clomiphene) and gonodotropins ( inje may be added to slightly boost follicle quality
This approach sits between true natural cycle IVF and conventional IVF, offering slightly better control while still avoiding full ovarian stimulation.
Who Is a Good Candidate for Natural Cycle IVF
Natural cycle IVF is not right for everyone. It works best for specific patient profiles:
- Women with diminished ovarian reserve who produce few eggs even with stimulation medications
- Patients who cannot tolerate fertility drugs due to medical conditions or side effects
- Younger women with tubal factor or mild male factor infertility who prefer a less invasive approach
- Patients who prefer to avoid creating multiple embryos for personal, ethical, or religious reasons
Natural cycle IVF is generally not recommended for women over 40 unless other options have been exhausted, as per-cycle success rates drop significantly with age.
Success Rates and Expectations
| Age group | Success rate per cycle (natural IVF) | Success rate per cycle (conventional IVF) |
| Under 35 | 7 to 15% | 40 to 50% |
| 35 to 39 | 5 to 10% | 30 to 40% |
| Over 40 | Below 5% | 15 to 25% |
Key points to consider:
- Per-transfer success rates (when an embryo is actually transferred) are higher, often 20 to 30%, because cycle cancellations are excluded
- Multiple cycles may be needed: Patients undergo an average of 3 to 4 natural IVF cycles before achieving a live birth
- Cycles can be repeated monthly with no rest period required, unlike conventional IVF
- Cumulative success over several natural cycles can approach conventional IVF rates for select patients
Why Patients Choose Markham Fertility Centre for IVF
- Personalized protocols: Your physician selects the approach (natural, modified, or conventional) based on your age, ovarian reserve, and goals
- Pain-free egg retrieval with an anesthesiologist at every procedure, the only clinic in Ontario to offer this and it is included in the cost of IVF and it is at NO extra cost for OFP-funded IVF cycles
- On-site genetics program for patients who transition to conventional IVF and need PGT
- Five locations across Markham, Barrie-Innisfil, Oshawa, Orillia, and Sudbury
- Ontario Fertility Program participant for funded IVF cycles
Learn more about IVF options at Markham Fertility Centre →
FAQ
Is natural cycle IVF cheaper than conventional IVF?
Yes. By eliminating fertility medications ($3,000 to $7,000 per cycle), natural cycle IVF costs significantly less per attempt. However, lower per-cycle success rates may require more cycles, which can offset some of the savings. In addition, Markham Fertility Center has a lower price per IVF cycle for natural or modified IVF.
Can I do genetic testing (PGT) with natural cycle IVF?
Typically no. PGT requires multiple embryos to be useful, whereas natural-cycle IVF usually produces only one. However, if genetic testing is important to you, you can do genetic testing on your only embryo.
How many natural IVF cycles can I do in a row?
Because no high-dose stimulation is involved, you can begin a new natural cycle immediately without a rest period. Many patients complete back-to-back cycles monthly.
What happens if no egg is retrieved?
This is a known risk of natural cycle IVF. If the follicle is empty or ovulation occurs before retrieval, the cycle is cancelled. You can try again with your next menstrual cycle at no additional stimulation cost.