Influence of incubator type on embryo development and clinical outcomes: A retrospective cohort study comparing time-lapse benchtop incubators versus big box incubators

Research Question: Do embryo development and pregnancy outcomes differ between patients whose embryos were cultured in a time-lapse benchtop incubator compared to a conventional big box incubator? Design: Clinical outcomes of 2,198 patients whose embryos were cultured in a time-lapse benchtop incubator or a conventional big box incubator were compared retrospectively. Patients undergoing their first IVF or ICSI cycle between 2017–2020 were included. To account for baseline differences and potential confounding factors, inverse probability weighting (IPW) was applied. The confounders used are: female age, number of oocytes collected, treatment type, and number of embryos transferred. Results: Baseline imbalances observed in the raw data were successfully minimized after weighting with IPW, resulting in well-balanced groups. The primary outcome was defined as ongoing pregnancy rate (fetal heartbeat at 10–12 weeks). No significant differences were observed between the time-lapse benchtop group (n = 843) and big box group (n = 1355) for ongoing pregnancy rate (33.1% vs 31.9%) [IPW OR 1.00; 95% CI 0.82 to 1.21] or any other pregnancy outcome. The rate of transferred embryos displaying early cleavage on day 1 and optimal development on day 2 did not differ significantly. While the percentage of transferred embryos with ≥ 7 blastomeres on day 3 was significantly lower in the time-lapse benchtop group (87.1% vs 93.0%) [IPW OR 0.46; 95% CI 0.34 to 0.63], significantly more embryos were available for cryopreservation (59.5% vs 51.7%) [IPW mean difference 5.2; 95% CI 2.1 to 8.2]. Conclusions: In a well-controlled IVF laboratory environment, despite differences in intermediate laboratory outcomes, no differences in clinical success after fresh embryo transfer were observed between time-lapse benchtop and big box incubator systems. Key message: Our study indicates that the use of time-lapse benchtop incubators does not improve pregnancy outcomes compared with conventional big box incubators. Given the increasing adoption of time-lapse benchtop incubators, further evaluation of cumulative pregnancy outcomes and cost-effectiveness is needed to advance the responsible use of limited healthcare resources.