IVF rules have been tightened

Officials at the Human Fertilisation and Embryology Authority said there was no evidence to suggest there had been blunders at other IVF clinics.

Suzi Leather, its chairman, said: "This is a unique and clearly unfortunate case. We know of no other case where this has happened."

The British Fertility Society, which represents professionals working in reproductive medicine, backed that view.

In a statement, it said: "Errors are extremely rare."

It added: "Patients should be reassured that with over 25,000 treatments performed and over 7,000 babies born from IVF per year in the UK, incidents such as occurred in Leeds are exceedingly rare."

Learn from mistakes

Dr Alison Murdoch, chairwoman of the BFS, said the sector would learn from this case.

Errors such as this are extremely rare Sue Avery, Association of Clinical Embryologists

"Our sympathy goes out to all those involved in this case. Where errors occur we must learn from them, and as a matter of policy IVF units are continually reviewing their procedures to ensure that mistakes are not repeated."

The Association of Clinical Embryologists said it was also taking steps to ensure this case was never repeated.

Chairwoman Sue Avery said the association would be looking very carefully at the details of the report about the Leeds General Infirmary case when it was published.

"Although errors such as this are extremely rare in embryology, it is still vitally important that as a profession, we try to learn the lessons from this incident so that we can minimise the risks of any future recurrence," she said.

"In addition, we are also in the process of developing a professional code of conduct for our members, which will ensure as far as it is possible, that all embryologists adopt the same protocols and standards across the UK," she said.

"This will be yet another safeguard against accidents from occurring in future."

But Dr Sammy Lee, an embryologist, acknowledged that similar mix-ups could occur in the future.

"You can never say never and I think we have to acknowledge that human error is always possible."