OBJECTIVE: Unexplained infertility is defined by the absence of identifiable causes of infertility. The results of randomized studies and meta-analysis regarding the treatment of unexplained infertility are discordant due to methodological problems. DESIGN: The aim of this study is to compare the clinical pregnancy rate per cycle (CPR/c) in IUI and IVF/ICSI in cases of unexplained infertility, according to the woman's age group and to identify the factors which predict success. INTERVENTIONS: We performed a retrospective study in two ART centers, comparing overall clinical pregnancy, ongoing pregnancy and live birth rates in IVF/ICSI and IUI. We also compared pregnancy and birth rates according to different female age groups. RESULTS: 855 IVF/ICSI and 804 IUI cycles were compared. We found a significant difference (p < 0.001) in the pregnancy and live birth rates per cycle between IUI and IVF/ICSI, overall and in the different female age groups, except in women aged 40 and over. The greatest chances of pregnancy with IUI are found in women with secondary unexplained infertility, during the first two cycles and with a bi-follicular response to stimulation. In IVF/ICSI, pregnancy rates are higher in women with secondary unexplained infertility, in the first two cycles, in IVF and in women receiving a transfer of two embryos regardless of the embryonic stage. CONCLUSION: We recommend IVF/ICSI treatment rather than IUI for unexplained infertility (OR CPR/c 4.20 with 95% CI [3.72-4.68]). This is in accordance with NICE, which advises the use of IVF after 2 years.
OBJECTIVE: Unexplained infertility is defined by the absence of identifiable causes of infertility. The results of randomized studies and meta-analysis regarding the treatment of unexplained infertility are discordant due to methodological problems. DESIGN: The aim of this study is to compare the clinical pregnancy rate per cycle (CPR/c) in IUI and IVF/ICSI in cases of unexplained infertility, according to the woman's age group and to identify the factors which predict success. INTERVENTIONS: We performed a retrospective study in two ART centers, comparing overall clinical pregnancy, ongoing pregnancy and live birth rates in IVF/ICSI and IUI. We also compared pregnancy and birth rates according to different female age groups. RESULTS: 855 IVF/ICSI and 804 IUI cycles were compared. We found a significant difference (p < 0.001) in the pregnancy and live birth rates per cycle between IUI and IVF/ICSI, overall and in the different female age groups, except in women aged 40 and over. The greatest chances of pregnancy with IUI are found in women with secondary unexplained infertility, during the first two cycles and with a bi-follicular response to stimulation. In IVF/ICSI, pregnancy rates are higher in women with secondary unexplained infertility, in the first two cycles, in IVF and in women receiving a transfer of two embryos regardless of the embryonic stage. CONCLUSION: We recommend IVF/ICSI treatment rather than IUI for unexplained infertility (OR CPR/c 4.20 with 95% CI [3.72-4.68]). This is in accordance with NICE, which advises the use of IVF after 2 years.