Time plays a fundamental role in abortion regulation. In this article, we compare the regulatory frameworks in England and Wales and the Netherlands as examples of the centrality accorded to viability in the determination of the parameters of non-criminal abortion, demonstrating that the use of viability as a threshold renders the law uncertain. We assess the role played by the concept of viability, analysing its impact upon the continued criminalisation of abortion and categorisation of abortion as a medical matter, rather than a reproductive choice. We conclude that viability is misconceived in its application to abortion and that neonatal viability (relating to treatment of the premature infant) and fetal viability (related to the capacity to survive birth) must be distinguished to better reflect the social context within which the law and practice of abortion operate. We show how viability thresholds endanger pregnant people.