Aim of study: Over the last decade, laboratory procedures in in vitro fertilisation (IVF) have improved. Hyperstimulated ovaries cause an overload of surplus embryos. The present study was designed to evaluate the efficiency of two different modified IVF cycle protocols trying to reduce the load of medication used for IVF: simple IVF (S-IVF), Tamoxifen 40 mg daily from day 2 in the cycle to ovulation induction) and mild IVF (M-IVF), Tamoxifen 40 mg daily and every secondary 150 IU Gonal F until ovulation induction. The study aims to evaluate their efficiency compared with our conventional IVF (C-IVF) using a short antagonist protocol. Methods: A retrospective cohort study including all patients admitted to IVF for unexplained infertility, tubal factor, and male factor. In all stimulated cycles patients aimed at having fresh embryos transferred and surplus good embryos cryopreserved. All patients were recruited in the same period and allocated to the different treatments on their own request. The study was conducted between June 2019 and February 2021. Results: In total the study included 976 IVF cycles. 651 cycles from C-IVF, 145 cycles from S-IVF and 180 cycles from M-IVF. Mean age in the groups were comparable. Mean number of eggs retrieved was 6.1 (C-IVF), 1.2 (S-IVF) and 3.0 (M-IVF). Pregnancy rate per fresh transfer was found to be 29% for C-IVF, 26% in the S-IVF group and for the M-IVF 20%. Conclusion: Modified IVF stimulation protocols may be an important step towards a simpler assisted reproductive technology (ART) approach. More tolerable for women, easier and cheaper for patients and society they maintain acceptable clinical pregnancy rates. Large prospective studies need to be performed in the future.

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