Nearly half of children conceived at Netherlands fertility clinic have over 25 siblings

An investigation into a fertility clinic in Leiden, Netherlands, has further exposed the depth of problems children conceived there may be facing.

Earlier this year, it was discovered that the Leiden University Medical Centre’s (LUMC) sperm bank, closed in 2004, had missing data, and men fathering far more children than were legally allowed. Eight out of 1,141 children registered were found to have no father listed as donor. At least nine men were able to father more than 25 children, which was supposed to be the maximum, fathering over 400 children just between those nine men.

New details have since emerged that are even more disturbing. It has since been discovered that 440 children have over 25 brothers or sisters, also conceived at the facility using donor materials, and even more children have no listed father.

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“The results of the research so far show that of the 1173 descendants, 440 descendants have more than 25 half-brothers/sisters. But it has also become clear that there is a lot we do not yet know or cannot find out. For example, it is not possible to determine from which donor the donor sperm was used for 102 descendants,” LUMC said in a statement, adding, “The people involved feel cheated.”

LUMC director Martin Schalij also acknowledged that the investigation, conducted in 2023, revealed that there were serious issues, but affected people were not informed. “The report also showed that there were clues before 2023 indicating that the administration was incomplete,” Schalij said. “We realize that with the knowledge we have now, we should have reacted to these clues to inform the people involved. We deeply regret that we did not do this.”

A 1992 law dictated that donors could father no more than 25 children between 12 women, as a means to avoid accidental incest. That, Schalij acknowledged, is a real possibility, as most of the donors and the women who used the sperm bank live around the same area.

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