Morphology still matters when selecting euploid embryos: inner cell mass (ICM) and trophectoderm (TE) are predictive of pregnancy outcomes

Morphologic grading of embryos has been an ART standard for nearly 4 decades. More recently, PGT-A has improved embryo selection. Data conflicts regarding whether morphological evaluation improves outcomes of euploid embryo transfers [1, 2, 3]. Our objective was to determine whether morphology is predictive of pregnancy outcomes among single thawed euploid embryo transfers (STEETs). Retrospective cohort study. We reviewed all STEETs at a university-based ART center from 2014-2018. STEETs were excluded if oocytes were cryopreserved, embryos were created at another facility, embryos were frozen or biopsied twice, PGT-M or -SR was used, or an oocyte donor or gestational carrier was used. Only the first STEET during the study period that did not meet any exclusion criterion from each patient was included. Embryo morphology was graded according to Gardner [4]. Outcomes included implantation rate of all transfers and live birth (LB) rate, excluding 154 ongoing pregnancies and 28 pregnancies with unknown birth outcomes. Statistical analysis included chi-square, one-way ANOVA, and 2 multivariable log-binomial regression models to determine the association of predictors (age, expansion, ICM, TE) with implantation and LB. We reviewed 1323 STEETs (mean age 37y; range 24-46y). Overall, implantation was 69% and LB (n=1141) was 55%. ICM and TE were bivariately associated with both implantation and LB (p<0.01), but age and expansion were not. ICM significantly predicted implantation, but TE did not. Both ICM and TE independently predicted LB (see Table for adjusted predicted probabilities of implantation and LB based on ICM and TE grades at mean levels of all covariates in the models). Ploidy status is not the sole determinant of embryo competence. ICM and TE are strong predictors of LB and can improve selection among euploid embryos. Poor ICM is the greatest negative morphological predictor of implantation and LB. Our model can serve as a counseling tool for patients banking embryos.Tabled 1Morphological ParameterCountsProbability of Implantation (95% CI)Probability of LB (95% CI)ICM-A18172%(65 – 79%)57%(50 – 65%)ICM-B108870%(67 – 72%)55%(52 – 59%)ICM-C5437%(24 – 51%)31%(18 – 44%)TE-a3771%(57 – 85%)67%(51 – 84%)TE-b114969%(67 – 72%)56%(52 – 59%)TE-c13759%(50 – 67%)43%(34 – 52%)Combined Effect of ICM+TE:---ICM-A + TE-a2375%(61 – 89%)71%(55 – 87%)ICM-B + TE-a1473%(58 – 87%)68%(52 – 86%)ICM-A + TE-b15873%(66 – 80%)59%(51 – 67%)ICM-B + TE-b95071%(68 – 74%)57%(53 – 60%)ICM-C + TE-b4138%(24 – 52%)32%(18 – 45%)ICM-B + TE-c12460%(51 – 69%)44%(35 – 53%)ICM-C + TE-c1332%(20 – 44%)25%(13 – 36%)No combinations of ICM-A + TE-c or ICM-C + TE-a were present in the sample so these probabilities are not shown. Open table in a new tab