Experts are warning that the long-term safety of screening embryos for genetic diseases is going unchecked.
Preimplantation genetic diagnosis (PGD) is a way of checking that an embryo is free of inherited diseases before it is put into the womb to grow.
PGD is a relatively new procedure and was first introduced in 1990 as an experimental procedure. It involves removing a cell from an embryo when it is around three-days old and experts are saying that not all babies born after PGD are being followed up to check for any adverse effects this might have.
Since 1990 it is estimated that more than 1,000 babies have been born following PGD and licences have been granted for PGD to screen for the genetic form of cystic fibrosis and Huntington's disease.
In November 2001, the Human Fertilisation and Embryology Authority (HFEA) agreed on conditions in which PGD could be used under the Human Fertilisation and Embryology Act (1990) and in line with the results of a public consultation on the acceptability of PGD.
It is said that PGD can also be used to check for an inherited form of bowel cancer called familial adenomatous polyposis and that embryos can also be selected purely because they are a tissue match for a sick sibling.
There are eight centres in the UK that currently offer PGD to couples from families with a strong history of inherited diseases and about 100 cycles of PGD are carried out there each year. Worldwide there are about 1,000, according to the HFEA.