Scientists are developing a technique called in vitro gametogenesis or IVG to generate synthetic gametes for research and, potentially, for treating infertility. What would it mean for feminist concerns over the future of reproductive practice and biotechnological development if egg and sperm cells could be produced in laboratory conditions? In this article, I take on the question by discussing the emerging technique of IVG through the speculative feminist analysis of ambiguous reproductive futures. Feminist cultural and science studies scholars have explored the transformative effects of biomedicine on reproduction through science fiction novels and other cultural products. I theorise the speculative and visionary in biomedicine in the context of ethnographic methodology by drawing on ‘thought experiments’ conducted with stem cell scientists as shared acts of future-oriented contemplation. I develop the figure of SF proposed by Donna Haraway to investigate how science facts and speculative fabulation together shape futurities of reproduction. I propose including shifting frontiers in feminist thinking of the SFs in bioscience. Biomedical research aims to shift the borders between what is known and not known in reproductive biology, subsequently raising new technical, ethical and political issues in terms of stratified reproduction. The article shows that synthetic gametes are anticipated to intensify selective procreation. Simultaneously, IVG is seen to forge new biogenetic relationships and possibilities for non-normative reproduction and kin-making. Following Haraway, I argue that by ‘staying with the trouble’ of these biotechnological visions, feminist speculative analytics on technoscience offers a valuable tool to envision more hopeful and equal futures together with scientists.