This study examines the underlying assumptions that influence attitudes towards the prevention of disabled lives through the use of reproductive genetic technologies. I consider the models of disability and demonstrate that the way in which we think about disability is important in the 'real world.' As my analysis shows, the debate about models of disability is relevant to law because legal provisions adopt these models. I highlight the dominance of the medical model, and suggest that the law pays insufficient regard to the interests of disabled people because a flawed model is being used. I explore the expressivist argument advocated by disability rights supporters. This argument holds that assumptions are implicit in the accepted practice of prenatal testing and the selective abortion of foetuses with detected impairments. Disability is a complex social construct and the way society constructs disability communicates signals regarding the value society places on its disabled members. The Abortion Act 1967 s1(1)(d) is focused on as an example of the expressivist nature of law arguing that it reflects societal values that construe aborting a 'disabled' foetus as more justifiable than aborting a 'normal' one. This study demonstrates the link between the way disability is perceived and the laws that result from those attitudes. It is also clear that when the law takes a disablist position, it encourages people to share these assumptions about the lives of disabled people. It has been possible to identify consistent expression of values all based on the medical model and therefore disablist because they rely on negative assumptions. By analysing a variety of contexts, I draw attention to the way values infiltrate different spheres of life. I highlight the disablist nature of prenatal diagnosis, exploring the way in which disablist values are expressed in law making processes and professional rhetoric.