A final investigation report found that a laboratory worker at the former Foundation Medical Center for Birth Control (SMCG) in Leiden fathered 16 children with his own sperm between 1979 and 1984, rather than the previously reported 11. He had recorded the sperm under the names of other donors. The man, who died last year aged 81, was found to have carried mutations associated with deafness and loss of balance, as well as a CFTR mutation that can cause cystic fibrosis if both parents are carriers.

Seven of the children said they were disappointed by the report and believed more children may have been conceived with the man's sperm. They called for people conceived at SMCG during the period to come forward, while questioning whether the 1984 cutoff was sufficiently supported. About 100 people have contacted the clinic in recent years. MC Kinderwens said the investigation was complete because no new information had emerged, but that the case was not closed and that it would remain a contact point for those involved.