Recent scientific advances mean the widespread introduction of non-invasive prenatal diagnosis (NIPD) for chromosomal aneuploidies may be close at hand, raising the question of how NIPD should be introduced as part of antenatal care pathways for pregnant women. In this paper we examine the ethical implications of three hypothetical models for using NIPD for aneuploidy in state-funded healthcare systems and assess which model is ethically preferable. In comparing the models we consider their respective timings; how each model would fit with current screening and diagnostic tests offered to pregnant women; the implications of offering NIPD at different stages of pregnancy; and the potential for each model to support reproductive autonomy and informed decision-making. We conclude by favouring a model that would be offered at 11-13 weeks gestation, alongside existing combined screening, provided that this is accompanied by measures to maximise informed decision-making, for example provision of adequate pre- and post-test counselling. Key words: Genetic Screening/Testing, Genetic Counselling/Prenatal Diagnosis; ethics; aneuploidy; Down syndrome. ; This article was written by Dr Ainsley Newson during the time of her employment with the University of Bristol, UK (2006-2012). Self-archived in the Sydney eScholarship Repository with permission of Bristol University, Sept 2014.