Drawing on scholarship from ignorance studies, this paper uses the case of the UK debates on mitochondrial donation (2012–2015) to emphasize the importance of deploying an analysis of ignorance that goes beyond medical and safety concerns when scrutinizing debates or campaigns around new reproductive technologies. In contrast to what happened with previous reproductive health treatments or drugs, the potential medical risks of mitochondrial donation were explicitly acknowledged and examined during its public and parliamentary discussions. However, I show, using the concepts of ‘acknowledged unknowns’ and ‘ignored knowns’, how the attention drawn to the medical risks contributed to obscuring the assessment of its economic and social impacts by silencing key knowledge regarding the limitations of mitochondrial donation in relation to the potential beneficiaries, the scope of the techniques, their alternatives and their costs. This article therefore calls for more systematic use of an integrated analytical framework of ignorance to be applied in the field of reproductive public policies, paying particular attention not only to the ways that medical risks are addressed, but also to the type of knowledge and disciplines this allows to silence or side-line in the framing and assessment of new biotechnologies. © 2021