Unexplained Total Fertilization Failure after Intracytoplasmic Sperm Injection Cycles: A Case-Control Study on Predictive Factors and Retreatment Prognosis

BACKGROUND: The aim of our study was to detect the rate of unexplained total fertilization failure (TFF) after intracytoplasmic sperm injection (ICSI) and identify its risk factors and retreatment prognosis. MATERIALS AND METHODS: In this retrospective case-control study, we searched the computerized database of the Royan Institute (Tehran, Iran) from March 2015 to March 2019 and retrieved all cases diagnosed with TFF after ICSI. TFF cases that did not have any recognized risk factors were classified as unexplained (subgroup A). Cases with recognized risk factors were classified as subgroup B. The control group was randomly selected from infertile couples who underwent ICSI cycles with fertilization of at least one oocyte during the same time interval. Characteristics and treatment outcomes of the cases with unexplained TFF (subgroup A) were compared to the control group, and to the other TFF cases (subgroup B). RESULTS: Out of 18,750 couples who underwent ICSI cycles, 296 (1.58%) experienced TFF for the first time. Of these, 49 (16.5%) couples were diagnosed as unexplained TFF (subgroup A) and 247 (83.5%) were placed in subgroup B, TFF with expected risk factors. Multivariable logistic regression analysis showed that the total number of mature oocytes (P<0.001), duration of infertility (P=0.043), and women’s body mass index (BMI, P<0.001) were significant predictive factors for unexplained TFF. In the ICSI cycle after TFF, clinical pregnancy and live birth rates in subgroup A were higher than subgroup B. Although differences between these groups were not statistically significant (P=0.14 and P=0.07, respectively), this finding could be clinically important. CONCLUSION: Unexplained TFF following ICSI is a rare event significantly related to a lower number of mature oocytes, longer duration of infertility and higher female BMI. It has a good prognosis in retreatment cycles in comparison with expected TFF cases. Clinicians should take this into consideration for patient counseling and management.