In the UK, putative fathers are encouraged to be involved in antenatal and maternal health care, in the belief that involving men as early as possible lays the foundation for better, more involved fatherhood. Integrating men into maternity care can, however, have hitherto unexplored ethical complexities. We begin by providing three ethical justifications for involving men in antenatal and maternity health care, and then discuss how each necessarily constrains the nature of this involvement. The medical setting itself creates some of the difficulties. This observation leads us into a broader exploration of the medicalisation of men's transition to fatherhood.