The European Society of Human Reproduction and Embryology (ESHRE) called for a continent-wide cap on donor conceptions at its London conference, citing cases where single donors have fathered hundreds of children. Dutch donor Jonathan Meijer contributed sperm used to conceive between 550 and 600 children before a court ordered him to stop in 2023. Genetic testing services including 23andMe and Ancestry have erased donor anonymity, enabling donor-conceived people to discover vast sibling networks — some numbering in the hundreds.

National limits vary wildly: Malta and Cyprus allow one child per donor, the UK permits 10 families, and Denmark allows 12. Yet Denmark exports most of its sperm; over half of UK donations in 2020 were imported, primarily from Denmark and the US. This cross-border flow makes national caps ineffective. ESHRE proposes an initial 50-family limit per donor across Europe, with a long-term target of 15 families. Professor Jackson Kirkman-Brown of the University of Birmingham argues only a transnational limit works, though researcher Vasanti Jadva warns even 15 may be too high.

The stakes go beyond identity. A Danish donor with a cancer-linked genetic mutation fathered at least 197 children across Europe; some developed cancer and died. US guidance suggests 25 births per 800,000 people, but many American banks self-limit at 25 families. Advocate Ties van der Meer, chair of Stichting Donorkind, pushes for five families domestically and two internationally. ESHRE's proposal marks a starting point, but enforcement across jurisdictions remains the core challenge.