Embryo gene tests do no harm

Carrying out genetic tests on embryos appears to have no effect on the health of the resulting children, according to a new US study. Scientists at three institutes pooled their data on all PGD (preimplantation genetic diagnosis) babies born during the past 12 years, a total of 754. The research, reported in the journal Fertility and Sterility, showed that babies born following PGD are no more likely to be affected by birth defects than babies conceived naturally. Although they found a slightly higher incidence of conditions such as Down syndrome and cleft lip and palate, they attribute this increase to the higher average age of women who undergo PGD.

PGD was first carried out in 1990, and has since resulted in the birth of over 1000 babies worldwide. It involves removing a single cell from an early embryo created using in IVF usually at the eight-cell stage of development. It is used to detect the presence of gene mutations that cause a particular genetic disorder (or to determine sex in the case of conditions that affect only boys), so that only unaffected embryos are returned to the womb.

The new study combined data from the three centres that have performed PGD most often: the Reproductive Genetics Institute in Chicago, St Barnabas Medical Centre in New Jersey, and SISMER in Bologna, Italy. The findings allay fears that the technique could harm the embryo and the resulting child, raised after earlier, smaller studies suggested a slightly higher rate of birth defects. Commenting on the results, UK fertility expert Mohammed Taranissi told the Times newspaper: 'It's always been the case that we have not seen problems with PGD, but it is good to see a large study like this that reflects this experience worldwide'.

Recently, the UK's HFEA changed its policy to allow the use of PGD to help couples conceive 'saviour siblings': babies who are a tissue match for an existing sick child, in cases where the embryo is tested solely for tissue type, and not for a genetic disease. A spokeswoman for the HFEA welcomed the US research, saying: 'This new study further supports our policy decision and means that all potential parents who use PGD to avoid serious disease can be reassured that the test is not harming their babies'.