Efficacy of natural cycle IVF: a review of the literature.

Since the introduction of IVF treatments, natural cycle IVF has been largely replaced by IVF with ovarian stimulation. However, natural cycle IVF has several advantages. It is associated with a close to zero multiple pregnancy rate, and a zero risk of ovarian hyperstimulation syndrome. Per cycle, natural cycle IVF is less time consuming, physically and emotionally less demanding for patients, and cheaper than stimulated IVF, but also less effective. This systematic literature review addresses the issue of effectiveness of natural cycle IVF. Herein, 20 studies describing natural cycle IVF are presented; 12 case series and eight in which a comparison was made between natural cycle IVF and IVF with ovarian stimulation. Good-quality randomized controlled trials and formal cost-effectiveness analyses are lacking. The 20 selected studies comprised a total of 1800 cycles of natural cycle IVF, resulting in 819 embryo transfers (45.5% per cycle) and 129 ongoing pregnancies (7.2% per cycle and 15.8% per embryo transfer). Efficacy of natural cycle IVF is hampered by high cancellation rates because of premature LH rise and premature ovulations. It is concluded that natural cycle IVF is a low-risk, low-cost and patient-friendly procedure. A randomized controlled trial comparing natural cycle IVF with current standard treatment strategies is warranted.