Allowing couples who cannot conceive naturally to have babies through artificial fertilisation could alter human evolution, according to a leading fertility researcher.
Dr Hans Hanevik, who heads the fertility department at Norway's Telemark Hospital, claims in-vitro fertilisation, otherwise known as IVF, means humans will become increasingly reliant on artificial help to conceive.
He says detective genes that normally die with the carrier are being passed on, leading to future generations needing the same help to have children.
And the birth of millions of babies could alter the course of human evolution, he is expected to tell the European Society of Human Reproduction and Embryology (Eshre).
At the conference in Vienna next month he will say babies could be being born with the defective genes that led to their parent's difficulty having children.
As those babies grow up and try to reproduce, the defect will spread, and they will need similar help to have their own children.
In the abstract for the conference Dr Hanevik wrote: 'In accordance with the principle of evolution, subsequent generations will thus be genetically adapted to an environment in which reproduction is increasingly dependent on technological intervention.'
Some 300,000 babies have been born through artificial fertilisation since 1991 and IVF accounts for more than one in 40 of the 750,000 babies born annually in the UK.
And as more babies are born the change in genetics will be enough to alter the human genome, Dr Hanevik claims.
'IVF is not just a treatment for infertility, but also a technological intervention at the point in a human life cycle where natural selection operates at its strongest,' he added.
'Although it is a great medical achievement, it circumvents a range of reproductive barriers.'
But many couples who find it difficult to conceive actually have 'plumbing' issues rather than any genetic defect, says Gill Lockwood, medical director of Midland Fertility Services.
The clinic was the first in the UK to achieve live births from the mothers' own eggs.
She added: 'Women may have fallopian tubes blocked by appendicitis and men may have undescended testicles or have had a vasectomy.
'IVF can overcome these problems. Even if they do have gene problems is that a reason to stop them being parents? IVF can bring delight and joy to people who finally get a baby — and to the siblings, grandparents, aunts, uncles and so on.'
However, Hanevik has stressed he is not criticising IVF, and is instead urging more discussion about what it may do to future generations.
In a previous paper he has claimed the long-term affects of IVF have not been studied due to an unwillingness to look at it from the perspective of evolution.
'To point out that IVF may favour disease-prone individuals or lead to reduced fitness over generations could surely be provocative, but is worth considering.'
In 2017 nearly 55,000 patients had 75,000 treatments, with 93 per cent having basic IVF.
Just 22 per cent of these led to live births and this low success rate has been linked to the genetic defects that caused infertility, according to data from the Human Fertilisation and Embryology Authority.