The increase in birth defects in babies born after assisted conception could be partly due to underlying fertility problems, according to an Australian study.

The analysis, believed to be the most comprehensive of its kind, looked at the outcomes of 308,974 births in Southern Australia between 1986 and 2002, 6,163 of which used assisted reproductive techniques. They found that 8.3 percent of children born using assisted conception had some kind of birth defect, compared with 5.8 percent in those conceived naturally.

However, after adjusting the data to take into account other risk factors that could lead to birth defects, the University of Adelaide team found no significant increase in risk for babies conceived with in IVF.

But there was still a significant increase in risk for those conceived using ICSI (intracytoplasmic sperm injection), a technique to overcome male infertility. Author Professor Michael Davies attributed this to the fact that ICSI selects a single sperm and that this could be 'seriously defective' and if so it might 'never naturally fertilise an egg'. IVF allows sperm competition, and is therefore more similar to natural conception, he said.

In addition, the study found that women with a history of fertility problems, but who didn't have fertility treatment in order to conceive, were more likely to have children with birth defects.

'This, combined with the finding that those using ICSI also had slightly elevated risks of birth defects, suggest that the underlying problem that led them to seek medical assistance in the first place is likely contributing to the elevated risk of birth defects in their children', Dr Glenn Schattman, President of the Society for Assisted Reproductive Technology said in a statement.

The study, published in the New England Journal of Medicine, also found that there was no significant difference in risk between the use of fresh or cryopreserved embryos in either IVF or ICSI.

Professor Joe Leigh Simpson, President-elect of the International Federation of Fertility Societies, said that while this study was interesting, they needed to consider if results from a generation ago are still relevant.

'We should also take this work seriously; it highlights the need for continued vigilance, perhaps especially with ICSI. Parents need to be counselled individually, but we need to keep things in perspective; the vast majority of births after assisted conception show no problems', he said.

Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.