Does the time interval from the end of sperm processing to intrauterine insemination (lab-to-uterus time) affect treatment outcome?

BACKGROUND Intra-uterine insemination is an essential component in the treatment of infertility. Success rates are dependent on clinical factors of the female partner, sperm quality, and preparation technique. The effect of the time interval between the end of sperm preparation in the lab, and its injection into the uterine cavity (lab-to-uterus time) is yet to be determined. AIM To investigate the association between the lab-to-uterus time and the pregnancy rate. MATERIALS AND METHODS Partner and donor spermatozoa intra-uterine insemination cycles were included. Preparation for intra-uterine insemination of partners' fresh ejaculate or donor thawed spermatozoa was identical. The time interval from the completion of this stage to the actual intra-uterine injection was recorded. The lab-to-uterus intervals were divided into groups A (0-29 min), B (30-59 min), C (60-89 min), and D (90-180 min). Pregnancy was defined as two adequate consecutive doubling levels of hCG and the pregnancy rates were compared between the groups. RESULTS A total of 267 female patients (138 partner spermatozoa, 129 donors) who had 470 intra-uterine insemination cycles (218 partner spermatozoa, 252 donors) were included. No significant differences in pregnancy rates per treatment cycle were found between the four lab-to-uterus interval groups: A (n = 96 cycles; 16.7%), B (n = 217; 19.4%), C (n = 121; 16.5%), and D (n = 36; 36.1%). No difference was found in the pregnancy rates between partner and donor spermatozoa. In the case of fresh partner spermatozoa, the pregnancy rates for groups were as follows: A (n = 40 cycles, 20%); B (n = 94; 14.9%), C (n = 70; 17.1%), and D (n = 14; 35.7%) (NS). In the case of thawed donor spermatozoa, the pregnancy rates (per cycle) for groups were as follows: A (n = 56; 14.3%), B (n = 123; 22.8%), C (n = 51; 15.7%), and D (n = 22; 36.4)% (NS). CONCLUSIONS The intra-uterine insemination outcome was not affected by the lab-to-uterus time interval. Extended waiting up to 3 h for insemination did not have any detrimental effect on pregnancy rates, regardless if partner or donor spermatozoa was used.