In natural cycle IVF the oocyte that is released during the normal monthly cycle is collected, without administering medication to stimulate the ovary.

In certain cases, a low dose of hormones is administered during the last days of the treatment to avoid early ovulation.

This therapy is mostly indicated for women who cannot or do not wish to undergo ovarian stimulation. It is also recommended for women with very poor ovarian response in a  previous attempt. It is a milder treatment compared with the usual ovarian stimulation cycle. Since the ovaries are not artificially stimulated, the patient can repeat the procedure again next month. Finally, the cost of the procedure is lower.

The basic drawback of natural cycle IVF is that it generally has a significantly lower success rate compared with other treatments due to the small number of collected eggs. This cancels out the advantage of being less expensive, since, on average, more attempts are necessary to achieve a pregnancy.

Natural cycle IVF or Ovarian stimulation protocol?

The dilemma confronting several young couples who are interested in IVF treatment is whether it would be best to undergo natural cycle IVF instead of a stimulated one.

To answer this problem one should look at statistics. In cases of women, where the collection of 2-3 oocytes during oocyte retrieval is predicted, ovarian stimulation is recommended. The increased number of oocytes that we collect after ovarian stimulation subsequently increases the number of embryos which are suitable for transfer. The increased number of available embryos for transfer allows us to select the highest quality embryos.  This option is not available in natural cycle IVF.

It is particularly restrictive, regarding fertilisation potential and a positive outcome, to invest all our hopes in a single oocyte. As our aims regarding fertility increase, so does the possibility of finding quality embryos for transfer.

However, in cases of ovarian insufficiency, where the use of gonadotropins is fruitless, the choice of a slightly modified natural cycle is considered a wise choice. We refer to a modified natural cycle due to the uncertain outcome of a completely natural cycle. The administration of drugs for mild stimulation from day 6-7 of the cycle, combined with the administration of the antagonist can increase the chances for a successful outcome.

There may be times where these types of therapies are more economically advantageous although they have lower success rates.