Plans to extend the screening of embryos for genetic mutations linked to hereditary breast cancer have caused a split in the Dutch coalition government. Ethical questions have been raised because for the first time in the Netherlands preimplantation genetic diagnosis will be available for mutations if the chance of developing the disease, the “penetrance,” is less than 100%.

Preimplantation genetic diagnosis is used in combination with in vitro fertilisation to select healthy embryos for reimplantation in the womb. Screening is already permitted for genetic conditions such as Huntington’s disease and cystic fibrosis, which have 100% penetrance. The new plan would …