胚胎发育潜能的评估及其研究进展

在体外受精一胚胎移植（IVF—ET）技术中,人类的配子和胚胎存在大量浪费的现象,如约20％的卵子不受精、约35％的胚胎被直接作为废弃胚胎而丢弃、约60％胚胎在体外培养过程中不能发育到囊胚。即使胚胎被移植入子宫,也是大部分不能着床。人类胚胎的低利用率除了与超排卵、体外培养、胚胎评估、选择方法和内膜容受性等有关外,还与人类自身的生理状况相关。在自然状态下,生育年龄妇女每周期的妊娠率也仅为25％～35％,而流产率则高达10％～15％。

Evaluation of embryonic development potential and its research progress

To improve the clinical pregnancy rate and reduce multiple pregnancy rate at the same time, more powerful evaluation methods are needed for selecting embryos with high developmental poten- tial. The value of pronuclear scoring is still in dispute. Our opinion is that pronuelear scoring can only partly reflect the embryonic developmental potential, therefore combination with scoring system on cleav- age stage is indispensable. The variations of blastomere number, mononuclearity in the blastomeres and blastomere size were still independently significant, which was demonstrated in one study for analyzing embryos in either no implantation or twin implantation retrospectively. However, even embryos with poor morphology have certain development potential, while good morphology is not the guarantee of pregnancy. It was proved in a study that half of blastocysts had chromosome abnormalities detected by array based comparative genome hybridization （CGH）. Alternative non-invasive techniques have been proposed, which may be able to detect alterations of the culture environment surrounding embryos. One of the most re- cently applied approaches is to measure metabolomic changes in the culture medium. Advance in time-lapse observation technology also make full monitoring of embryos possible. Although the results of these initial investigations are promising, further prospective studies are required to define clearly the potential benefits and most relevant applications of this novel non-invasive technology in the field of assisted reproduction. [Key words] Embryo; Pronuclear scoring; Blastocyst; Metobolomics