Comparison of Pregnancy Outcomes Between Fresh Embryo Transfer in a Natural IVF Cycle and IUI Cycle Among Infertile Young Women

BACKGROUND: The purpose of the current study was comparing pregnancy outcomes for natural cycle in vitro fertilization (IVF) per fresh embryo transfer (ET) and oocyte pick-up (OPU) in intrauterine insemination (IUI). METHODS: This was a retrospective cohort study of women who underwent either IUI (n=246) or OPU with fresh ET for natural cycle IVF (n=291), conducted between April 2017 and February 2018 at the Center for Reproductive Medicine and Implantation Research, Sugiyama Clinic Shinjuku, Tokyo, Japan. Patients in both groups did not receive ovarian stimulation and luteal support; gonadotropin-releasing agonist spray was administered 35 hr before OPU or IUI. The clinical pregnancy rate was compared between the IUI and IVF groups. Data analysis was based on the number of cycles. The p≦0.05 was considered significant. RESULTS: The clinical pregnancy rate per OPU in the IVF group was higher than the one in IUI group (20.6% vs. 10.1%), and the difference was significant (p<0.01). The pregnancy rate for natural cycle IVF calculated per fresh ET was 36.8%. The miscarriage rate did not significantly differ between the IVF (4.1%) and IUI (8.0%) groups. CONCLUSION: Fresh ET in natural cycle IVF provides a higher implantation rate than IUI.