Hidden camera footage
Many British couples are choosing the sex of their babies at clinics abroad, which often offer the procedure illegally, the BBC has learned.
Representatives from one Turkish fertility clinic, the Jinemed Center, were secretly filmed when they came to London to see prospective patients.
They guaranteed if pregnancy occurred it would be of the chosen sex.
Sex selection is illegal in Turkey and in the UK. The clinic, which denies wrongdoing, is now being investigated.
The Turkish government, which is carrying out the inquiry into the Jinemed Center, has warned patients not to travel there for the treatment.
The Center told its prospective patients during a London visit that there was a big demand for gender selection from UK couples.
The BBC's Colette McBeth said it was possible to almost guarantee the sex of a baby using IVF and a type of embryo screening called Pre-Implantation Genetic Diagnosis (PGD).
But in most countries PGD is only used for medical reasons, our reporter added.
She said: "Some countries do allow sex selection like the US and Russia but I quickly realised there was a problem with all of this.
"Many patients who were planning to go abroad were completely confused as to where it was legal and where it wasn't."
The Jinemed Center denies it offers sex selection and says it always warns patients about the risks of multiple pregnancies.