New rules on sperm donation have come into force in the Netherlands to prevent men fathering hundreds of children by registering with multiple clinics.

A national register and a system of codes has been set up to enforce the limit of 12 families per donor.

Each donor is given a personal code and 12 maternal codes, which are used up every time a woman conceives using his sperm. Once all 12 codes have expired, the man is unable to donate sperm again.

The limit of 12 families was already written into Dutch law, but there was no mechanism to enforce it or the previous limit of 25 children because disclosing the identity of donors was seen as breaching their privacy.

Ties van der Meer, chair of child protection charity Stichting Donorkind, told NOS: “Because the rules were not properly enforced in the beginning, there was a high risk of incest. Some donor children were unable to go dating without being worried because they didn’t know how many half-brothers or sisters they really had.”

Netflix series

The best known mass donor is Jonathan Jacob Meijer, the subject of the Netflix documentary The Man With 1000 Kids, who was taken to court by Stichting Donorkind to stop him donating sperm.

Meijer got around the limits by contacting 11 different clinics and using the Danish sperm-by-post service Cyros. The new rules will not stop donors registering in other countries.

Last year Leiden University’s teaching hospital LUMC admitted that some 440 people had more than the permitted number of 25 donor siblings as a result of administrative problems at its sperm bank. One man fathered 86 children.

Stichting Donorkind said it had identified 10 doctors who used their own sperm to father more than the permitted number of children, including Jan Karbaat, who produced at least 81 children with mothers who used his fertility clinic.

The new rules will enable the public health system to ensure the limits are maintained without compromising the anonymity of donors.

The limit of 25 donor children was changed in 2018 so families could have more than one child from the same person.