Abstract
Objective:To determine if Day 7 blastocysts merit biopsy, vitrification and transfer consideration by contrasting their aneuploidy and implantation rates to Day 5 and 6 blastocysts.Methods:A total of 1,925 blastocysts were biopsied from 402 PGT-A cycles over a 12 to 16 month interval. All embryos were cultured under tri-gas, humidified conditions (37ºC) for up to 7 days (168 hours post-insemination). Biopsied blastocysts were vitrified and trophectoderm samples analyzed using NextGen sequencing. Single euploid embryo transfers were performed (n=254) using either a Day 5 (n=145), Day 6 (n=92) or a Day 7 blastocyst (n=16) post-warming. Euploidy rates and pregnancy outcomes were subsequently assessed and differences determined by day of development and blastocyst quality grade.Results:No differences were observed in implantation, pregnancy loss or ongoing pregnancy rates between Day 5 and Day 6 blastocysts. Development to Day 7 accounted for 6.6% of all blastocysts. Euploidy rates were higher in Day 5 blastocysts (53.5%; p<0.05) compared to Day 6 (40.4%) and Day 7 (35.9%). High implantation potential (56.3% to 79.3%) of vitrified-warmed euploid blastocyst occurred independent to the day of development. However, miscarriage/loss rates increased (22.2% vs. 2%; p<0.05) with Day 7 blastocysts, resulting in lower (p<0.05) live birth rates (43.8% vs. 67.4-77.2%).Conclusion:Culturing blastocysts to Day 7 has proven beneficial by achieving viable euploid embryos that would have otherwise been discarded. An extra Day of embryo growth allows select patients additional opportunities for in vitro development and possible healthy term live births.
Highlights
Human in vitro blastocyst development is highly dependent on variables inherent to the laboratories culture environment (Gardner, 2016; Swain et al, 2016)
In lieu of the pioneering blastocyst culture efforts of Yves Menézo in the 1990's, investigators are again questioning if 144 hours of in vitro culture is an accurate measure of developmental potential when implementing routine blastocyst culture for all patients (Kovalevsky et al, 2013; Capalbo et al, 2015)
Human blastocyst culture efforts revealed that Day 7 blastocysts possessed reduced viability, but were capable of creating live births (Veiga et al, 1999; Richter et al, 2006)
Summary
Human in vitro blastocyst development is highly dependent on variables inherent to the laboratories culture environment (Gardner, 2016; Swain et al, 2016). Human blastocyst culture efforts revealed that Day 7 blastocysts possessed reduced viability, but were capable of creating live births (Veiga et al, 1999; Richter et al, 2006). A healthy baby is the end goal for any patient choosing to invest time, money and emotion into assisted reproductive technologies (Heijnen et al, 2004). For this goal to be realized a blastocyst must first be available
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