Intracytoplasmic sperm injection versus conventional in vitro insemination in couples with non-male infertility factor in the 'real-world' setting: analysis of the HFEA registry.

Background: In assisted reproductive technology (ART), the choice between intracytoplasmic sperm injection (ICSI) and conventional in vitro insemination (IVF) remains a pivotal decision for couples with female or unexplained infertility. The hypothesis that ICSI may not confer significant improvements in live birth rates in the absence of a male infertility factor was explored in this study.

Methods: This was a retrospective collection of data recorded by the Human Fertilisation and Embryology Authority (HFEA) in the UK from 2005 to 2018 and analysed through regression analysis models on both the entire dataset and a matched-pair subset. First fresh ART cycles were analysed according to the insemination technique in order to compare live birth as the main outcome. Cycles were included if complete information regarding infertility cause, female age, number of oocytes retrieved, allocation to ICSI or IVF, and treatment outcome in terms of live birth was available. Matching was performed at a 1:1 ratio between IVF and ICSI cycles according to the cause of infertility, female age, number of oocytes, and year of treatment.

Results: This study, based on 275,825 first cycles, revealed that, compared with IVF, ICSI was associated with higher fertilization rates and lower cycle cancellations rates. However, ICSI was associated with a lower chance of implantation and live birth than IVF in cycles with female-only infertility: in the entire dataset, the adjusted odds of having a live birth decreased by a factor of 0.95 (95% CI 0.91-0.99, p = 0.011), while in the matched-pair analyses it decreased by a factor of 0.91 (95% CI 0.86-0.96, p = 0.003) using ICSI compared to IVF. For unexplained infertility cycles, the adjusted odds ratios for live birth in ICSI compared to IVF cycles were 0.98 (95% CI 0.95-1.01) in the entire dataset and 0.97 (95% CI 0.93-1.01) in the matched-pair analysis.

Conclusions: Compared with IVF, ICSI was associated with a reduction in live births when ART was indicated due to female-only factors. Additionally, no significant improvements were associated with the use of ICSI in cycles with unexplained infertility. Our findings impose a critical reevaluation regarding the use of ICSI over IVF for cases with female-only factors and unexplained infertility.