RESUMEN
<p><b>OBJECTIVE</b>To investigate the factors that affect the clinical pregnancy rate after intrauterine insemination (IUI).</p><p><b>METHODS</b>We retrospectively analyzed the clinical data of 611 IUI cycles and analyzed the relationship of the clinical pregnancy rate after IUI with the female age, infertility duration, type of infertility, cycle number, cycle protocol, thickness and type of endometrium, and semen parameters before processing.</p><p><b>RESULTS</b>The clinical pregnancy rate was significantly higher in the ovulation induction than in the natural ovulation cycles (23.03% vs 11.03%, P < 0.01), but lower in the 4th cycle and above than in the 1st, 2nd, and 3rd cycles (2.04% vs 21.30%, 18.13%, and 12.67%, P < 0.01). Marked decreases were found in the clinical pregnancy rate in the females aged ≥ 40 years and the cases with pre-processing total progressively motile sperm count (TPMSC) < 10 x 10(6), progressive motile sperm < 20%, or morphologically normal sperm < 2% (all P < 0.05). Logistic regression analysis revealed the cycle protocol, cycle number, and percentage of progressively motile sperm as three predictive variables affecting the clinical pregnancy rate after IUI (P < 0.05).</p><p><b>CONCLUSION</b>The cycle protocol, cycle number, percentage of progressively motile sperm, female age, TPMSC, and sperm morphology are the main factors affecting the clinical pregnancy rate following IUI, while infertility duration, type of infertility, and thickness and type of endometrium exert little influence.</p>