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Background: In modified natural cycle IVF (MNC-IVF), treatment is aimed at using the one follicle that spontaneously develops to dominance, using a GnRH-antagonist together with gonadotrophins in the late follicular phase only. The MNC-IVF is of interest because of its low-risk and patient-friendly profile. The effect of application of MNC-IVF preceding standard IVF with ovarian stimulation on overall results is unknown., Methods: This single-center cohort study provides follow-up of an earlier study in which nine cycles of MNC-IVF were offered to 268 patients. Ongoing pregnancy rates and live birth rates, as well as time-to-pregnancy after controlled ovarian stimulation-IVF (COS-IVF) following MNC-IVF, were evaluated., Results: Actual observed cumulative ongoing pregnancy rates and live birth rates after sequential treatment with MNC-IVF followed by COS-IVF were 51.5 (95% CI: 45.4-57.6) and 50.0% (95% CI: 43.9-56.1) per patient, of which 8.0 and 6.7% were twins. Median time to ongoing pregnancy was 28.8 weeks. Including treatment-independent pregnancies, cumulative ongoing pregnancy rate was 56.7% (95% CI: 50.7-62.8)., Conclusions: Sequential treatment with MNC-IVF followed by COS-IVF does not appear to compromise overall success rates, while twin pregnancy rate is low. Because of its patient-friendly and low-risk profile, it seems appropriate to perform MNC-IVF preceding COS-IVF.

Background: In minimal stimulation IVF, treatment is aimed at using the single oocyte that spontaneously develops to dominance. To prevent untimely ovulation, a GnRH antagonist is administered in the late follicular phase of the natural cycle together with recombinant FSH for substitution. Owing to the lack of ovarian stimulation, minimal stimulation IVF is a low-risk and patient-friendly treatment. In this study, effectiveness of minimal stimulation IVF was studied., Methods: In this prospective multicentre cohort study, minimal stimulation IVF was offered to 350 patients. All indications for conventional IVF were included. Main outcome measures were pregnancy rates per cycle and cumulative pregnancy rates after three cycles., Results: A total of 336 patients completed 844 cycles (2.5 per patient). The overall ongoing pregnancy rate per started cycle was 8.3% [95% confidence interval (CI) 6.4-10.2%]. The cumulative ongoing pregnancy rate after up to three cycles was 20.8% (95% CI 16.4-25.3%) per patient. No differences were found according to indication for IVF., Conclusions: Minimal stimulation IVF seems suitable for all indications studied. Pregnancy rates are encouraging. Owing to the low-risk and patient-friendly nature of this protocol, it seems a feasible treatment option for patients requiring IVF.

Background: The use of the natural cycle for IVF offers the advantage of a patient-friendly and low-risk protocol. Its effectiveness is limited, but may be improved by using a GnRH antagonist to prevent untimely LH surges., Methods: In this pilot study, minimal stimulation IVF with late follicular phase administration of the GnRH antagonist cetrorelix and simultaneous substitution with recombinant FSH was applied for a maximum of three cycles per patient. Main outcome measures were pregnancy rates per started cycle and cumulative pregnancy rates after three cycles., Results: A total of 50 patients completed 119 cycles (2.4 per patient). Fifty-two embryo transfers resulted in 17 ongoing pregnancies [14.3% per started cycle; 32.7% per embryo transfer; 95% confidence interval (CI) 7.9-20.7% and 19.7-45.7%, respectively]. One dizygotic twin pregnancy occurred after transfer of two embryos, the other pregnancies were singletons. The cumulative ongoing pregnancy rate after three cycles was 34% (95% CI 20.6-47.4%). Live birth rate was 32% per patient (95% CI 18.8-45.2%)., Conclusions: Pregnancy rates after IVF with minimal, late follicular phase stimulation are encouraging. Considering the low-risk and patient-friendly nature of this protocol, it may be a feasible alternative to IVF with ovarian hyperstimulation.