Children conceived by IVF (in-vitro fertilisation) or sperm injection have twice the risk of being born with a major birth defect.

When sperm injection was introduced in 1992, there were fears that it came with a far higher risk of birth defects, although the findings from early studies did not back up this concern.

Now, however, a new study from Western Australia has definitively shown that the sperm injection procedure, as well as IVF, doubles the chances of defects.

The study team, from the University of Western Australia, compared the birth records of children born by IVF or sperm injection with those conceived naturally. They discovered that 8.6 per cent of the babies conceived by sperm injection, and 9 per cent of the IVF babies had major defects apparent after one year compared with 4.2 per cent of those conceived without technological help.

The researchers also found that those who had undergone assisted conception were also more likely to suffer multiple defects.

The reasons why this should be so are not easy to understand. It could have something to do with the relatively older age of the couples that seek assisted fertilisation, or it could perhaps be that the fertility drugs they have taken may have caused the defects. Another factor could be the assisted reproduction procedures themselves, such as the freezing and thawing of the embryos before implantation (N Engl J Med, 2002; 346: 725-30).