Terminology in this field is not uniform and it may be helpful to define some of the terms used in this chapter – and, in particular, to distinguish between experimental treatment, research and experimentation. Dickens 1 has defined an experimental treatment as a deliberate departure from orthodox therapy; given that medical orthodoxy itself is definable as a rule or procedure supported by an identifiable body of contemporary medical knowledge, this is as apt a description as any that could be formulated. The same author, however, points to the corollary: that a treatment cannot be experimental when there is no standard of orthodoxy; this must still apply to the majority of fetal treatments in utero. This chapter, however, is not concerned with treatment, which has been considered briefly already, but, rather, with research and experimentation – procedures which are not necessarily directed to the well-being of the individual subject. The distinction between research and experimentation is frequently blurred and, to some, may be non-existent. For present purposes, a research procedure is defined as one which is undertaken in the pursuit of knowledge or understanding within a defined prospective protocol or programme. An experiment, by contrast, can be regarded as designed to provide information of itself: it need not be preplanned and a useful experimental situation may arise fortuitously Much the same ethical rules will cover both procedures but nuances of difference may arise: for example, the quality of informed consent, discussed in Chapter 4, may be more exacting if the subject is asked to take part in a research programme which involves rigid schedules.