Before I was an embryo, I was a pre-embryo: or was I?

Issues surrounding human embryos are poignant and profound. Should research be conducted on them? Should they be discarded? Should they be donated to infertile couples? The Warnock Report was a landmark in providing guidelines limiting experimentation on human embryos to the first 14 days after fertilization, at which time implantation of the embryo is complete and the primitive streak has appeared. However, these embryological features were not considered sufficiently distinctive to bestow upon this 14-day period a separate classification. This situation changed when, in 1986, Anne McLaren suggested the use of the terms 'pre-embryo' or 'conceptus' to designate "the entire product of the fertilized egg up to the end of the implantation stage" and the term 'embryo' for "that small part of the pre-embryo or conceptus, first distinguishable at the primitive streak stage, that later develops into the foetus." In this paper we look critically at the term 'pre-embryo', and we shall present the case for an alternative set of terms, namely, embryo-placenta and embryo-fetus. We consider this latter to be biologically-based terminology, that does not have any connotation of restricted moral value as the term pre-embryo does for some.