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Objective: To investigate whether the morphodynamic characterization of a euploid blastocyst's development allows a higher prediction of a live birth after single-embryo-transfer (SET)., Design: Observational cohort study conducted in two phases: training and validation., Setting: Private in vitro fertilization centers., Patient(s): Euploid blastocysts: 511 and 319 first vitrified-warmed SETs from 868 and 546 patients undergoing preimplantation genetic testing for aneuploidies (PGT-A) in the training and validation phase, respectively., Intervention(s): Data collected from time of polar body extrusion to time of starting blastulation, and trophectoderm and inner-cell-mass static morphology in all embryos cultured in a specific time-lapse incubator with a continuous medium. Logistic regressions conducted to outline the variables showing a statistically significant association with live birth. In the validation phase, these variables were tested in an independent data set., Main Outcome Measure(s): Live births per SET., Result(s): The average live birth rate (LBR) in the training set was 40% (N = 207/511). Only time of morulation (tM) and trophectoderm quality were outlined as putative predictors of live birth at two IVF centers. In the validation set, the euploid blastocysts characterized by tM <80 hours and high-quality trophectoderm resulted in a LBR of 55.2% (n = 37/67), while those with tM ≥ 80 hours and a low-quality trophectoderm resulted in a LBR of 25.5% (N = 13/51)., Conclusion(s): Time of morulation and trophectoderm quality are better predictors of a euploid blastocyst's reproductive competence. Our evidence was reproducible across different centers under specific culture conditions. These data support the crucial role of morulation for embryo development, a stage that involves massive morphologic, cellular, and molecular changes and deserves more investigation., (Copyright © 2019 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Time-lapse microscopy (TLM) is an exciting novel technology with great potential for enhancing embryo selection in the embryology laboratory. This non-invasive objective assessment of embryos has provided a new tool for predicting embryo development and implantation potential. TLM detects several morphological phenomena that are often missed with static observations using conventional incubators, such as irregular divisions, blastocyst collapse and re-expansion, timing of blastocoel appearance, and timing of formation and internalization of fragments. Nevertheless, it should be recognized that conventional morphological assessment has been widely accepted as the gold standard by most embryologists. TLM can enhance conventional morphological assessments to improve embryo selection and subsequent reproductive outcomes. Furthermore, morphokinetic parameters can aid in differentiating between euploid and aneuploid embryos, although they are not sufficiently accurate to replace preimplantation genetic testing for aneuploidy. Morphokinetic assessment together with chromosomal screening may ultimately help identify euploid embryos with the highest developmental potential., (Copyright © 2017 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Over the past four decades we have witnessed great progress and increasing pregnancy success rates with in vitro fertilization. However, this apparent success has been accompanied by the burden of multiple pregnancies. While efforts to reduce the number of embryos transferred have had a salutary impact on the incidence of high order multiple pregnancies, twin gestations have not diminished significantly. Thus, the search for a marker of embryo quality with the goal of selecting the single best embryo for transfer continues to be the major challenge facing our field. The four contributions in this Views and Reviews present several contemporary approaches, both invasive and non-invasive, for evaluating embryo viability. Each group makes the case that recent techniques, including time-lapse microscopy, biomechanical markers for oocytes and embryos, novel non-invasive methods of evaluating embryo metabolism and function as well as measurement of mitochondrial DNA, will allow the identification of the single best embryo for transfer. They describe several promising markers of embryo viability, although the goal of finding the "holy grail" of embryo selection has not yet been realized., (Copyright © 2017 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Objective: To characterize atypical dynamic embryo phenotypes identified by time-lapse microscopy, evaluate their prevalence, and determine their association with embryo development., Design: Retrospective multicenter cohort study., Setting: Five IVF clinics in the United States., Patient(s): Sixty-seven women undergoing IVF treatment with 651 embryos., Intervention(s): Embryo videos were retrospectively analyzed for atypical phenotypes., Main Outcome Measure(s): Identification of four groups of atypical embryo phenotypes: abnormal syngamy (AS), abnormal first cytokinesis (A1(cyt)), abnormal cleavage (AC), and chaotic cleavage (CC). Prevalence and association with embryo morphology and development potential were evaluated., Result(s): A high prevalence of atypical phenotypes was observed among embryos: AS 25.1% (163/649), A1(cyt) 31.0% (195/639), AC 18% (115/639) and CC 15% (96/639). A high percentage of embryos with atypical phenotype(s) had good quality on day 3 (overall grade good or fair): AS 78.6% (70/89); A1(cyt) 79.7% (94/119), AC 86.4% (70/81), and CC 35.2% (19/54), but the blastocyst formation rates for these embryos were significantly lower compared with their respective control groups: AS 21.5% vs. 44.9%, A1(cyt) 21.7% vs. 44.6%, AC 11.7% vs. 43.1%, and CC 14.0% vs. 42.3%., Conclusion(s): Embryos exhibiting atypical phenotypes are highly prevalent in human embryos and show significantly lower developmental potential than control embryos., Clinical Trial Registration Number: NCT01369446., (Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)