Maternal physiology and blastocyst morphological grade correlate with an inherent difference in human peri-implantation developmental potential.

Our group has been using an extended embryo culture (EEC) system to culture human embryos for up to an additional 7 d to study peri-implantation over the past three years. Since similar EEC parameters were measured for these projects, we performed a retrospective analysis of 653 human embryos to determine what maternal factors correlate with peri-implantation developmental outcomes. Frozen day five or day six human blastocysts donated for research (WIRB study no. 1179872) were warmed, dezonated, and cultured in vitro up to EEC day seven following an established protocol (Deglincerti et al., Nature 2016). The trophectoderm outgrowth area, total cell number, epiblast cell number, and human chorionic gonadotropin (hCG) production in spent media were measured during EEC. Patient information including maternal BMI, age, infertility diagnosis, FSH, LH, FSH: LH ratio, estradiol, and anti-müllerian hormone (AMH) levels on menstrual cycle day 3, and an antral follicle count (AFC) were used in our analysis. Additionally, blastocysts with the highest morphological grade that typically yield live birth rates above 65% (Good Quality) were compared with those of lower morphological grade that typically yield less than 55% live birth rate (Fair Quality), based on our historical data. We then used a spearman correlation coefficient to assess the strength of the association between the aforementioned maternal factors and extended culture parameters. A chi-squared analysis was used to compare binomial outcomes with categorical predictors. T tests or ANOVA’s were used for comparing two or multiple continuous variables from categorical predictors respectively. Several maternal physiological influences during oocyte development (age, BMI, and FSH: LH, AMH, AFC) were significantly correlated with extended culture outcomes (p<0.05). Embryos with high morphological grade had significantly increased outgrowth areas compared to those with low morphological grade (Good Quality: 0.17 ± 0.02; Fair Quality: 0.12 ± 0.02, p<0.05). Maternal age was correlated with hindered EEC measurements in both the non-donor fertility patients as well as in healthy donors. When comparing embryos with the highest morphological grade only, advanced maternal age (35+ years old) still contributed to decreased hCG production (p<0.05) and hindered epiblast formation compared to those from younger patients (<35 years old, p<0.01). In conclusion, we show that human EEC may be valuable in predicting post-transfer developmental potential. Additionally, maternal physiology during oocyte development including age, BMI, and FSH: LH, AFC, and AMH significantly correlates with the peri-implantation developmental potential of human embryos.