preimplantation embryo

pre·im·plan·ta·tion em·bry·o

(prē-implan-tāshŭn embrē-ō) Implantation begins on the seventh day after fertilization; preimplantation is from day 1 to day 6; some clinicians and lawyers use the term "pre-embryo" for this period, implying that the embryo has not formed.