The effect of rapid and delayed insemination on reproductive outcome in conventional insemination and intracytoplasmic sperm injection in vitro fertilization cycles.

Purpose: The precise timing of insemination after oocyte retrieval is sometimes challenging. In this study, we have assessed the effect of the variation in insemination timing on reproductive outcome for both conventional insemination (CI) and intracytoplasmic sperm injection (ICSI) cycles.

Methods: A single-center retrospective cohort data analysis was performed on 6559 patients (9575 oocyte retrievals) from January 2017 to July 2019. The main outcome measured was live birth rates. Secondary outcomes included fertilization rate per all oocytes retrieved, blastocyst utilization, clinical pregnancy, and miscarriage rates. The time interval between oocyte retrieval and insemination was analyzed in eight categories: 0 (0- < 0.5 h), 1 (0.5- < 1.5 h), 2 (1.5- < 2.5 h), 3 (2.5- < 3.5 h), 4 (3.5- < 4.5), 5 (4.5- < 5.5), 6 (5.5-6.5), and 7 (6.5- < 8 h). The number of retrievals in each group (0-7) was 586, 1594, 1644, 1796, 1836, 1351, 641, and 127 respectively.

Results: The mean fertilization rate for CI ranged from 54.1 to 64.9% with a significant difference between time categories 0 and 5 (p < 0.001) and 1 and 5 (p < 0.0.001). The mean fertilization rate for ICSI ranged from 52.8 to 67.3% with no significant difference between time categories. Blastocyst rate for CI and ICSI was not significantly different. Miscarriage and clinical pregnancy rates in CI and ICSI were not significantly different. Live birth rates differed significantly (p < 0.05) in CI with time categories 0 and 7 representing the lowest rates, but not in the ICSI group.

Conclusion: If performing CI or ICSI before 1.5 h and > 6.5 h, any detrimental effects are moderate on fertilization but do not affect blastocyst usage and birth rates.

Trial Registration: Institutional Review Board Approval from the Beth Israel Deaconess Medical Centre [IRB Protocol #: 2015P000122].