In a shocking revelation, the administration of the Leiden University Medical Centre’s (LUMC) sperm bank, which ceased operations in 2004, has been exposed as a chaotic mess. Eighty of the 1,141 children conceived there have been unable to identify their biological fathers; nine donors fathered over 400 children.

This crisis brought to light a violation of a 1992 rule limiting sperm donors to fathering no more than 25 children, distributed among 12 women, to prevent incest and inbreeding. But donors far exceeded this limit, with one siring nearly 90 children. Martin Schalij, a member of the LUMC’s board of directors, expressed concern, stating that the risk of hereditary defects resulting from half-siblings having romantic relationships is “certainly not zero.”

The problem of prolific and secretive sperm donors is not new. The most recent scandal in the Netherlands involved a laboratory worker at a Leiden fertility clinic who clandestinely fathered at least 11 children with his own sperm between 1979 and 1984, without being registered as a sperm donor. The notorious fertility doctor Jan Karbaat fathered at least 80 children and gynaecologist Jan Wildschut about 60 in the 1980s and 1990s.

Ties van der Meer, of Stichting Donorkind, a foundation advocating for the interests of individuals conceived through sperm donation, said that this crisis at the LUMC may only be the “tip of the iceberg”. He called for a comprehensive review of all hospital archives.