EMBRYO DEVELOPMENT ON DAY 7 BY CULTURE MEDIA EXPOSURE: A PROSPECTIVE TRIAL

Abstract

1) To test the hypothesis that slowly developing embryos on day 6 (D6) will be more likely to develop into good, biopsy-quality embryos when randomized to fresh culture medium on D6, compared to embryos that remain in the same medium until day 7 (D7) and that this is age-dependent; 2) To determine the overall percentage of otherwise discarded D6 embryos that would meet biopsy criteria on D7 in PGT-A cycles. Prospective randomized trial within an academic IVF clinic. Embryos of patients ages 18-44, undergoing fresh autologous or donor cycles, with or without preimplantation genetic testing (PGT) that did not meet criteria for biopsy and/or freeze on D6, were randomized to remain in the culture medium (Global® total; GLBT) used for D3-D5 of culture (C-GLBT) or be moved to fresh medium (F-GLBT) with re-evaluation on D7. Embryos from the same cycle were randomized to the medium groups following a pre-determined algorithm. Cycles with at least 2 randomized embryos were included. Log binomial regression was used to calculate the relative risk and 95% confidence intervals of embryos achieving good quality on D7 when exposed to fresh versus continuous media. The models accounted for patients contributing embryos from more than one cycle. 1254 embryos were randomized between 3/2019 – 2/2020, with complete grading available for 603 embryos cultured in F-GLBT and 620 cultured in C-GLBT. The groups were similar for patient age, gravidity, parity, AMH, BMI, infertility diagnosis, stimulation protocol and mature eggs retrieved. The proportion of good quality D7 blastocysts did not differ between media groups (10.1% (61/603) vs. 9.7% (60/620), F-GLBT vs. C-GLBT, respectively; RR 1.05 [95% CI 0.74 – 1.47]). No significant differences were found between groups when stratified by age (Table). In PGT cycles, 12.3% (26/211) of embryos in F-GLBT achieved good quality on D7 compared to 10.3% (22/214) in C-GLBT, RR 1.20 (95% CI 0.72 – 2.00). 9.9% of embryos otherwise discarded on D6 met criteria for biopsy and/or freeze on D7. Relative risk of conversion to good quality blastocysts on D7 after randomization to fresh or continuous media on D6, stratified by ageTabled 1F-GLBTN (%)RR (95% CI)C-GLBTN (%)RR (95% CI)Total (F-GLBT + C-GLBT)N (%)RR (95% CI)<38N = 89750/446 (11.2%)Ref41/451 (9.1%)Ref91/897 (10.1%)Ref≥38N = 32611/157 (7.0%)0.63 (0.32–1.23)19/169 (11.2%)1.24 (0.69–2.22)30/326 (9.2%)0.91 (0.57–1.44) Open table in a new tab Refreshment of medium on D6 did not increase the incidence of D7 good, biopsy quality embryos and this was not influenced by patient age. However, our findings support culturing slow developing embryos to D7, rather than discarding them on D6, as a significant number of good quality blastocysts become available for clinical use.