A US clinic has sparked controversy by offering would-be parents the chance to select traits like the eye and hair colour of their offspring.
The LA Fertility Institutes run by Dr Jeff Steinberg, a pioneer of IVF in the 1970s, expects a trait-selected baby to be born next year.
His clinic also offers sex selection.
UK fertility experts are angered that the service will distract attention from how the same technology can protect against inherited disease.
The science is based on a lab technique called preimplantation genetic diagnosis, or PGD.
This involves testing a cell taken from a very early embryo before it is put into the mother's womb.
Doctors then select an embryo free from rogue genes - or in this case an embryo with the desired physical traits such as blonde hair and blue eyes - to continue the pregnancy, and discard any others.
Dr Steinberg said couples might seek to use the clinic's services for both medical and cosmetic reasons.
For example, a couple might want to have a baby with a darker complexion to help guard against a skin cancer if they already had a child who had developed a melanoma. But others might just want a boy with blonde hair.
His clinic is offering this cosmetic selection to patients already having genetic screening for abnormal chromosome conditions in their embryos.
"Not all patients will qualify for these tests and we make NO guarantees as to 'perfect prediction' of things such as eye colour or hair colour," says the clinic's website.
Dr Steinberg said: "I would not say this is a dangerous road. It's an uncharted road."
He said the capability to offer such services had been around for years, but had been ignored by the medical community.
"It's time for everyone to pull their heads out of the sand."
But Dr Gillian Lockwood, a UK fertility expert and member of the Royal College of Obstetricians and Gynaecologists' ethics committee, questioned whether is was morally right to be using the science in this way.
"If it gets to the point where we can decide which gene or combination of genes are responsible for blue eyes or blonde hair, what are you going to do with all those other embryos that turn out like me to be ginger with green eyes?"
She warned against "turning babies into commodities that you buy off the shelf."
Josephine Quintavalle of Comment on Reproductive Ethics said: "This is the inevitable slippery slope of a fertility process which results in many more embryos being created than can be implanted. Choices will always have to be made. Do you choose octuplets or the ones with the prettiest noses?"
In the UK, sex selection is banned and choices are currently permitted only in relationship to the baby's health.
Italian fertility law does not permit the creation of surplus embryos or selective testing. Ms Quintavalle said that was "one sure way to avoid the slippery slope".
Meanwhile, new legislation in the UK, due to come in on 6 April, will allow IVF mothers to name anyone as "father" on the birth certificate - even another woman.
The only restriction on naming a second parent will be if they are close blood relatives or if the second person does not agree.