What is a Natural IVF Cycle?

If you are considering IVF treatment, you have probably read and have heard about the different types of IVF cycles. Most likely, you have also wondered how they differ and which one would be best for you.   It is important to realize that a women’s age is often the most important factor in determining reproductive potential. Overall health, medical history, and living habits also affect egg quality and reproductive potential.  All of this is taken into consideration when deciding which treatment may work best for you.  In recent years, minimal stimulation IVF cycles and natural IVF cycles have become popular.   In general, these types of IVF cycles are not as effective as traditional stimulated IVF cycles.  However, many people are still interested in these alternative IVF treatment cycles because of the lower cost.

Traditional IVF Cycle

Let’s start by defining and describing a “traditional” stimulated IVF cycle and clearing the air on the very misunderstood Natural IVF cycle.  A traditional IVF cycle begins with the start of gonadotrophins (injectable medications) to induce follicular growth and egg (oocyte) development.  The medications for the traditional cycle begin around the third day of the menstrual cycle and continue for approximately 8 to 12 days, depending on how the ovary responds to the medication.  Each traditional IVF cycle should be individualized so that patients will have different medication protocols based on their diagnosis and evaluation; thereby, optimizing the follicular development and ovarian response of the cycle.  When enough follicles have matured (ideal size approximately 18mm), the patient is given an injection of hCG (human chorionic gonadotropin) to induce egg maturation and to help time the egg retrieval.  The eggs obtained are then fertilized and can now be referred to as embryos. The embryos are cultured in the laboratory for 2 to 6 days and then transferred into the uterus where they implant and are the start  for the beginning of the pregnancy.

Natural IVF Cycle

A natural IVF cycle differs from a traditional cycle mainly in that there are no fertility drugs used to stimulate the follicles or eggs to grow.  Since no fertility drugs are used, typically only one follicle will mature producing one egg; therefore, the chances of becoming pregnant are much lower.  Likewise, there is a risk that the follicle will not produce a mature egg that can be used.  Close monitoring via transvaginal ultrasound and blood samples is needed to monitor the body’s natural menstrual cycle and follicle development.  The egg retrieval, egg fertilization, embryo culture, and embryo transfer processes are the same as a traditional IVF cycle.  The main difference between a natural IVF and a traditional stimulated IVF cycle is the lack of FSH (follicle-stimulating hormone) medication leading to the production of multiple mature follicles and eggs.

Patients choose a Natural IVF cycle for a number of reasons.  Commonly, patients choose this path for financial reasons or because they do not wish to have extra embryos remaining or cryopreserved (frozen for later use) should they become pregnant.  Since the goal of a traditional IVF cycle is to have multiple eggs and multiple embryos to enhance success rates, having extra embryos is common.  The cost associated with Natural IVF cycles is substantially less than traditional cycles, since the cost of medications, which constitute approximately half of the total cost of an IVF cycle, is greatly reduced.

Minimal Stimulation IVF Cycle

Another type of cycle that is a cross between the natural cycle IVF and the traditional stimulated IVF cycle is termed the minimal stimulation IVF cycle.  In a minimal stimulation cycle, a small amount of medication is given to induce some ovarian response.  The medication used may be oral, injectable or a combination of the two.  This cycle will typically result in more than one follicle and egg but less than could be obtained in a traditional IVF cycle.

Realizing that these cycles can be very complex and confusing, you should discuss with your provider the different types of cycles that are available and which type of cycle might benefit you most.

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