TROPHECTODERM MORPHOLOGY IN EUPLOID EMBRYOS IS RELATED TO INFERTILITY DIAGNOSIS AND PREGNANCY OUTCOME AFTER TRANSFER

A number of studies have shown that both day 3 and day 5 embryo morphology correlates with ongoing pregnancy rate and live birth rate. However, in the era of single euploid embryo transfer, few studies are available regarding effect of inner cell mass (ICM) and trophectoderm (TE) morphology on pregnancy outcomes after euploid transfer. We aimed to evaluate pregnancy outcomes, including live birth, as they relate to embryo characteristics and morphology. Retrospective chart review. We reviewed all single euploid embryos transfers in an academic fertility clinic by retrospective chart review from January 1, 2016 through August 31, 2018. Blastocyst morphology was evaluated by Gardner grading system. PGT-A was performed using a next generation sequencing platform. Variables assessed included blastocyst expansion level (EL), ICM grade, TE grade, patient age at retrieval, number of oocytes retrieved, infertility diagnosis, pregnancy (serum hCG), ongoing pregnancy (fetal cardiac activity) and pregnancy outcome. Logistic and linear mixed models with random intercepts to account for within-patient correlation were used to evaluate association between predictors and outcomes. All models were adjusted for age at retrieval and BMI. We evaluated embryo morphology in 341 single euploid embryo transfers including EL 3-6 (9 embryos were EL 3, 14 EL 4, 285 EL 5, 32 EL 6), ICM grade (136 A and 205 B), and TE grade (94 A, 222 B, 25 C). Pregnancy rate (positive serum hCG/total transfers) was only correlated with TE grade and was significantly lower in TE grade C (40%) transfers when compared to A and B (67%, 73%); (p=0.003, OR 0.3; 0.1-0.6). There was no difference in pregnancy rate between blastocysts frozen on day 5 vs 6. However, after a positive HCG, transfer of day 6 blastocyst was negatively associated with ongoing pregnancy (p=0.02; OR 0.3; CI 0.2-0.7). TE grade, ICM grade, and EL of blastocyst were not predictive of ongoing pregnancy after positive HCG. When TE grade C embryos resulted in pregnancy, subsequent live births were similar at 60% compared to grades A and B (71%, 62%). Of 12 spontaneous abortions in our cohort, there were none in the TE grade C group; unsuccessful pregnancies in this group were all classified as biochemical. The mean proportion of TE grade C embryos compared to total embryos created per fresh cycle was 17.4%. Unexplained infertility diagnosis was an independent predictor for a higher proportion TE grade C embryos per fresh cycle (p=0.02). There was no correlation between number of oocytes retrieved and proportion of TE grade C embryos. Euploid embryos with poor TE morphology occur more often in unexplained infertility. While pregnancy rate and initial HCG level is lower in embryos with poor TE morphology, ongoing pregnancy rates are similar, and live births occur. Setting appropriate expectations is key when counseling patients prior to single euploid embryo transfer. It is important that we understand subtle differences in expected outcomes based on embryo characteristics and morphology.