BACKGROUND: This study aimed to evaluate the effect of small intramural fibroids on the cumulative pregnancy, ongoing pregnancy, live birth and implantation rates after three IVF/ICSI attempts. METHODS: The first three treatment cycles of women enrolled for IVF/ICSI over a 12-month period were analysed. Only patients with small (<= 5 cm) intramural fibroids not encroaching upon the endometrial cavity were included in the fibroid group. Cox's hazards regression was used to estimate the hazard ratio (HR) associated with the presence of intramural fibroids. RESULTS: During the study period, 322 women without fibroids (control group) and 112 women with fibroids (study group) underwent 606 IVF/ICSI cycles. The pregnancy, ongoing pregnancy and live birth rates in the study group were 23.6, 18.8 and 14.8% compared with 32.9, 28.5 and 24% in the control group, respectively (P < 0.05). Cox regression analysis showed that the pregnancy rate at each cycle was reduced by 39% (HR = 0.61, 95% CI = 0.39-0.95, P = 0.029) in the study group compared with the control group. The cumulative ongoing pregnancy rate was reduced by 43% (HR = 0.57, 95% CI = 0.35-0.91, P = 0.018), and the cumulative live birth rate was reduced by 47% (HR = 0.53, 95% CI = 0.32-0.87, P = 0.013) in the study group. After adjusting for confounding variables, the presence of fibroids was found to significantly reduce the ongoing pregnancy rate at each cycle of IVF/ICSI by 40% (HR = 0.60, 95% CI = 0.36-0.99, P = 0.048) and the live birth rate at each cycle by 45% (HR = 0.55, 95% CI = 0.32-0.95, P = 0.03). CONCLUSION: Small intramural fibroids are associated with a significant reduction in the cumulative pregnancy, ongoing pregnancy and live birth rates after three IVF/ICSI cycles.