BackgroundInformation available to date regarding the pregnancy outcomes of intrauterine insemination (IUI) without ovarian stimulation (OS) in infertile patients with unilateral tubal occlusion remains scarce. The objectives of this study were to investigate for couples affected by unilateral tubal occlusion (diagnosed via hysterosalpingography (HSG)/transvaginal real-time three-dimensional hysterosalpingo-contrast sonography (TVS RT-3D-HyCoSy)) and male infertility: (1) whether significant differences exist in pregnancy outcomes between IUI with or without OS cycles, and (2) whether the pregnancy outcomes of IUI without OS in women with unilateral tubal occlusion were similar to those of women with bilateral patent tubes.Methods258 couples affected by male infertility completed 399 IUI cycles. The cycles were divided into three groups: group A, IUI without OS in women with unilateral tubal occlusion; group B, IUI with OS in women with unilateral tubal occlusion; and group C, IUI without OS in women with bilateral patent tubes. The main outcome measures, including clinical pregnancy rate (CPR), live birth rate (LBR), and first trimester miscarriage rate, were compared between either groups A and B or groups A and C.ResultsAlthough the number of dominant follicles > 16 mm were significantly higher in group B than that in group A (group B vs. group A: 1.6 ± 0.6 vs. 1.0 ± 0.2,P< 0.001), the CPR, LBR, and first trimester miscarriage rate were comparable between these two groups. When comparing group C to group A, the duration of infertility was significantly longer in group C than that in group A (group A vs. group C: 2.3 ± 1.2 (year) vs. 2.9 ± 2.1 (year),P= 0.017). Except for the first trimester miscarriage rate, which was significantly higher in group A (42.9%, 3/7) than that in group C (7.1%, 2/28) (P= 0.044), no significant differences were observed in the CPR and LBR in these two groups. After adjusting for female age, body mass index, and the duration of infertility, similar results were obtained between groups A and C.ConclusionsIn couples affected by unilateral tubal occlusion (diagnosed via HSG/TVS RT-3D-HyCoSy) and male infertility, IUI without OS might be an alternative treatment strategy. However, when compared to patients with bilateral patent tubes, the patients with unilateral tubal occlusion showed a higher first trimester miscarriage rate following IUI without OS cycles. Further studies are warranted to clarify this relationship.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12884-023-05705-3.