"Mini IVF"-Natural, Minimal Ovarian Stimulation (MOS), Modified Minimal Stimulation (MMOS) - Grace Fertility Centre " "

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“Mini IVF”-Natural, Minimal Ovarian Stimulation (MOS), Modified Minimal Stimulation (MMOS)

“Mini-IVF” was first introduced and practiced extensively by the late Dr. Osamu Kato in Japan and has since been promoted in a few other centres. Mini-IVF involves gentler ovarian stimulation protocols compared to conventional IVF approach, with greatly less medication, fewer injections, and, fewer but better quality eggs. Egg collection and all the subsequent steps are the same as for conventional IVF.


Added advantages of Mini-IVF are greatly reduced cost of treatment (from $3000-$5000), due to use of less drugs, and thus almost no side effects.


Who may benefit from Mini-IVF…more

  • Patients in their late 30s or 40s or those with poor ovarian reserve often have better ovarian response with this method
  • Any patient fearful of drug exposure and wanting a closer to “natural” approach.


More patience is required with this approach as multiple cycles may be needed to collect sufficient eggs to produce an “euploid” embryo (an embryo with normal chromosome number) that has a better chance of proceeding to a live birth. With advancing age, more embryos tend to be “aneuploid” (abnormal chromosome number) which is why miscarriages are more common with advancing age. See section on PGS



Factors involved in successful outcomes with Mini-IVF ….. more

Although this is a much simpler method for the patient, requiring less injections and blood tests, more care and attention is involved with the medical management in coaxing follicle development, reducing the possibility of premature ovulation and taking extra care in egg retrieval as in some cases, only one or two follicles may be retrievable on each occasion.

The use of medicine in mini IVF is often associated with a suboptimal endometrial lining and therefore the success of Mini IVF relies on good vitrification techniques such that the embryos can be frozen and transferred in a subsequent more normal cycle when the uterine lining is more receptive.



  1. What is Involved
    1. Natural cycles involve tracking an unstimulated normal cycle and retrieving the egg, from typically, one mature follicle.
    2. Minimal ovarian stimulation (MOS) involves the use of oral fertility medications alone while Modified Minimal Ovarian Stimulation (MMOS) uses some gonadotropin injections at the appropriate time to get possibly a few more mature eggs. While this may increase the number of mature eggs produced over a natural cycle or MOS cycle, it does not optimize the yield as in a fully stimulated standard IVF cycle
    3. Your age, ovarian reserve and other individual factors will influence your likely response to treatment and therefore the advice given on whether this would be a viable option for you.
    4. Natural, MOS or modified MOS cycles are not for everyone. It requires a very detailed discussion on the positive and negatives for each option.


    There is a growing need for fertility management for women in late 30s and early 40s who have diminished ovarian reserve seeking assisted conception and Mini-IVF has proved to be a useful approach in our experience. (See Patient Stories-“Dismissed as Perimenopausal”)