A special committee of gynecologists, embryologists, and ethicists instructed the fertility clinic Medisch Centrum Kinderwens (MCK) in Leiderdorp to inform parents about its mass donors in 2018. But the clinic also did so last year after the media reported about the 36 mass donors at MCK and the over 1,200 children they conceived, Nieuwsuur reports.

Mass donors are donors whose sperm were used to conceive more than 25 children. Investigation by Nieuwsuur last year revealed that the commercial clinic in Leiderdorp deliberately used the sperm of at least 36 men to father more than 25 children each, the most of any clinic in the Netherlands. These 36 men conceived at least 1,200 children with nearly 1,000 women. Earlier this year, Nieuwsuur also revealed that MCK used sperm from too old donors.

In 2017, several mothers discovered for themselves that a single sperm donor in the Netherlands had fathered at least 102 children. After that revelation, the Dutch Association of Gyneacologists (NVOG) established the “ad hoc committee on donor dilemmas” to investigate the matter.

The committee issued its advice in 2018, requiring clinics to conduct an internal analysis of the number of children per donor. “If it is determined that the number of 25 children per donor has been or will be exceeded, the (prospective) mothers and the donors should be informed of this by the clinic in question,” the recommendation states.

The NVOG board adopted all the recommendations, but the MCK failed to implement them and did not inform mothers and donors in 2018. Strikingly, two members of the MCK management team sat on the committee that made the recommendations: a gynecologist who no longer works at MCK and clinical embryologist and current director Wouter van Inzen.

MCK declined to comment to Nieuwsuur on why it remained silent about the 36 mass donors it deliberately created until the summer of 2025. Last year, the management stated: “It was decided at the time – in consultation with the professional group – not to actively approach people about this.”

The professional group, NVOG, denies this, adding that it adopted all of the committee’s recommendations, and these were not non-binding. “The premise was that clinics would follow the advice. The NVOG had and has no supervisory or enforcement role.”

The Ministry of Public Health was also aware of the advice since 2018, a spokesperson acknowledged to Nieuwsuur. Then-State Secretary Judith Tielen also mentioned the advice in a letter to parliament in September last year, but did not mention that clinics failed to act in 2018. The Health and Youth Care Inspectorate was also aware of the advice, but did not report on it. The Inspectorate is currently investigating MCK.

Stichting Donorkind, a foundation that advocates for the interests of children conceived through sperm donation, called it shocking that the Ministry and Inspectorate did not intervene eight years ago. The foundation called for an independent investigation into all the abuses surrounding donor conception in the Netherlands over the past years.

“The fact that the implementation of the advice was not monitored by the Inspectorate is extremely concerning. Furthermore, we find it particularly painful that donor children are not even mentioned in the advice,” the foundation said.

So far, 85 mass donors have been identified in the Netherlands. Most came from MCK (36), followed by Rijnstate (18). Several other clinics had one or two mass donors. Rijnstate already informed mothers and donors in 2014 and 2015.