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Mini IVF or Micro IVF?

by - 02.11.2010 | In Vitro Fertilization

Mini IVF refers to the use of non-injectible medications (mostly clomid) to mature 1-2 eggs for in vitro fertilization (IVF). Micro IVF is different from mini IVF because it involves the use of injectible FSH (follicle stimulating hormone) to induce mature and multiple eggs (5 eggs on average). Although they have been used interchangeably, mini IVF is not an ideal treatment because it does not result in higher pregnancy rates compared to intrauterine insemination (IUI) treatments. Pregnancy rates reported by clinics that offer mini IVF range from 0.8% to 9% per cycle depending on age groups. Therefore, we do not favor the use of clomid or clomid in conjunction with FSH for the purpose of IVF treatment due to low success rates.

Micro IVF on the other hand can be considered as a viable alternative option to IUI treatment in cases of early infertility. Micro IVF refers to the use of FSH to induce more than one mature egg and generally results in a favorable number of eggs for IVF. Although there is no set number of mature eggs needed for a healthy pregnancy, approximately 5 mature eggs are considered adequate response in micro IVF cycles.

Micro IVF is different from regular IVF cycles because it involves milder and less stimulation of the ovaries and unfortunately without the option of genetic screening of embryos for chromosomal abnormalities. Additionally, conventional fertilization is used instead of micro-injection of sperm called intracytoplasmic sperm injection (ICSI) with possible lower fertilization rates. In conventional IVF cycles, more eggs become mature and as a result more embryos are obtained. More embryos result in better chances because each embryo has a potential to make a baby. If there are multiple embryos on the 5th day of embryo development, 1-2 embryos can be transferred into the uterus and additional embryos can be frozen. Frozen embryos can be transferred in the event that the fresh cycle does not result in a pregnancy or another pregnancy is desired in the future. The practice of frozen embryo transfer has been an essential component of IVF for many years and the success rates are very similar to fresh IVF cycles.

A number of important variables are not observed or controlled for in IUI cycles compared to IVF cycles. Ovulation and the physical release of the egg is presumed to occur in IUI cycles, but in some cases of unexplained infertility the egg may be trapped in the follicle and the ovary. In IVF cycles, eggs are aspirated with a needle directly and observed under the microscope immediately eliminating the risk of a trapped egg inside the ovary.

Functionality of the fallopian tubes and spontaneous fertilization are also assumed to be normal in IUI cycles. The tubes may appear open or partially open on the x-ray test (Hysterosalpingogram – HSG), but they may not be functional in their ability to pick up and transport the egg into the uterus. Fertilization of the egg may also be an issue in IUI cycles even in the presence of normal semen parameters. This is generally attributable to poor sperm quality (not quantity) or a thick outer layer of the egg called zona which may prevent the entry of the sperm and fertilization.

Finally, embryo development can be observed up to six days in the incubator before transfer of embryos into the uterus. During this time, many parameters can be assessed and problems identified. In IUI cycles, such observation and diagnosis is impossible.

Overall, micro IVF may be an option for couples who suffer from infertility for at least one year along with the following criteria:

  • Reproductive age less than 35 and regular menstrual cycles
  • Normal semen parameters
  • Normal uterine cavity and open fallopian tubes
  • Normal egg reserve

Micro IVF is a not an option for the following group of patients:

  • Women of advanced reproductive age
  • Decreased ovarian/egg reserve regardless of age
  • Male factor infertility
  • History of recurrent pregnancy loss
  • Need for genetic testing of embryos such as CGH or PGD
  • Prior failed IVF treatment
  • Immunologic factors such as increased natural killer cell activity, DQ alpha or HLA match
  • Presence of advanced endometriosis

It would be important to discuss each infertility case in detail and evaluate thoroughly before deciding on the treatment option. For some couples, IUI treatment may still be a good initial approach, but in almost all cases of early infertility micro IVF would result in higher pregnancy rates. The cost and success rates of micro IVF are much lower than conventional IVF, but overall appear to be a better option compared to an IUI. All treatment options should be discussed with an infertility specialist.

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