A Christian charity has said it is concerned about safety and the ethics of new biotechnology after the birth of the UK's first baby that has the DNA of three people.
Mitochondrial donation treatment (MDT) uses healthy mitochondria from a female donor and is intended to prevent the transfer of incurable diseases from parents to children.
James Mildred, of Christian charity CARE, said the advent of MDT was "a source of some concern" and that an "ethical line" has been crossed.
He said there were a number of questions around the psychological impact on children and whether the development of MDT might lead to "designer babies".
"Evidence suggests that transferring nuclear DNA into a host donor egg cell is unsafe and could impact future generations," he said.
"The techniques used also lead to the destruction of human embryos, which raises moral questions.
"There are serious questions about how children will be affected. For example, nobody knows how a child will respond psychologically to the fact they have three parents.
"The biotechnology being used, whilst well-intentioned in this instance, also raises the spectre of 'designer babies'. It's clear an ethical line in the sand has been crossed that we come to regret deeply in years to come."