विवरण
Selection of embryos is a critical step in assisted reproductive technologies, aimed at identifying the healthiest and most viable embryos for transfer. Embryo selection involves analyzing the embryos' genetic makeup and morphology to increase the chances of a successful pregnancy. Preimplantation Genetic Testing (PGT) is one method used for embryo selection, allowing screening for genetic abnormalities before transfer. PGT can detect chromosomal abnormalities, single gene disorders, and structural rearrangements in embryos. Morphological assessment involves evaluating the embryo's appearance, cell number, and symmetry under a microscope.
Time-lapse imaging is a technique that provides continuous monitoring of embryo development, aiding in better selection decisions. Comprehensive chromosome screening techniques, such as array Comparative Genomic Hybridization (aCGH) and Next-Generation Sequencing (NGS), can be used for PGT. Embryo grading systems, such as the Gardner or Cummins criteria, help embryologists rank embryos based on their quality. Embryos selected for transfer should ideally have a high chance of implantation and lower risk of miscarriage.
सारांश
- The journey of embryo formation begins with gametogenesis, the creation of sperm and oocytes. These gametes fuse, initiating embryogenesis, a process marked by physical and biochemical events leading to a potentially transplantable embryo. Good quality gametes are essential for a healthy embryo. Oocytes can be graded based on morphological assessment, considering factors like cytoplasm expansion, cumulus cells, and membrane appearance.
- Embryo grading continues through different development stages. Day 1 involves assessing pronuclear alignment. From day 2 onward, factors like blastomere size and regularity, fragmentation presence, and cleavage rate are analyzed. By day 3, embryos should ideally reach the eight-cell stage, and grading continues based on cell size, arrangement, fragmentation, and cleavage timing.
- Blastocyst formation, typically around day 5, involves assessing expansion, hatching status, inner cell mass, and trophectoderm. Blastocyst grading systems like AA, BB, or CB help rank embryo quality, with 4AA being considered the highest. Culture to the blastocyst stage aims to select the embryo with the best developmental potential for transfer.
- Embryo selection is crucial to improve pregnancy rates, implantation success, and live birth outcomes. It helps reduce the incidence of miscarriages and multiple pregnancies. Strategies include sequential single embryo transfer, fresh or frozen embryo transfer, and minimal stimulation protocols to improve oocyte quality.
- Selection methods are broadly categorized into invasive and non-invasive techniques. Invasive methods, like polar body or embryo biopsy, allow for chromosome, DNA, gene expression, and proteomic analysis. These methods aim to identify and exclude embryos with genetic abnormalities. Non-invasive methods seek to achieve the same goal without harming the embryo.
- Invasive methods include polar body biopsy and blastomere or trophectoderm biopsy for preimplantation genetic screening (PGS) or diagnosis (PGD). These methods require genetic analysis to assess the genetic status of the embryo and prioritize genetically normal embryos for transfer.
- Non-invasive methods include manual reading, proteomics, and morphokinetics. Manual reading relies on microscopic observation of embryo morphology. Proteomics analyzes spent culture media for metabolites and consumption rates to assess embryo health. Morphokinetics involves time-lapse imaging to monitor embryo development in real-time.
- Morphokinetics provides real-time images of embryo development, allowing for observation of cleavage timing and other morphological changes. This method requires specialized incubators equipped with microscopes and cameras and relies on software and artificial intelligence to analyze the data.
- Although effective embryo selection improves chances of successful pregnancy outcomes, it is not 100% accurate. Limitations include high costs, the need for technically skilled personnel, time consumption, and the inability to improve embryo quality. These techniques assist in selecting the best embryo.
नमूना प्रमाण पत्र
वक्ताओं के बारे में
Dr Charudutt Joshi
Medical Director Genes India , ART Bank
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