The possibility of editing the genomes of human embryos has generated significant discussion and interest as a matter of science and ethics. While it holds significant promise to prevent or treat disease, research on and potential clinical applications of human embryo editing also raise ethical, regulatory, and safety concerns. This systematic review included 223 publications to identify the ethical arguments, reasons, and concerns that have been offered for and against the editing of human embryos using CRISPR-Cas9 technology. We identified six (...) major themes: risk/harm; potential benefit; oversight; informed consent; justice, equity, and other social considerations; and eugenics. We explore these themes and provide an overview and analysis of the critical points in the current literature. (shrink)