A study published last week in the journal Human Reproduction found an elevated risk of birth defects amongst babies conceived through assisted reproductive techniques, including IVF. The research, headed by Dr Jennita Reefhuis of the US Centre for Disease Control and Prevention, used data from the National Birth Defects Prevention Study to compare the health of babies born to women who had used the techniques with infants born to women who had conceived naturally.

Dr Reefhuis and colleagues found that babies conceived using assisted reproductive techniques are between two and four times more likely to have certain birth defects than those who were conceived naturally. They are twice as likely to be born with a cleft lip, four times as likely to have abnormalities of the oesophagus or rectum, and two to three times as likely to have cardiac defects. The researchers point out, however, that even with the increased risks birth defects are still uncommon in these babies.

All the births included in the study were single births, though multiple births are relatively common in assisted reproductive techniques. Multiple births in general are known to be at higher risk of birth defects, and this is one of the reasons that techniques such as IVF have previously been thought to be associated with a higher incidence of birth defects. This study also corrected for other factors such as the age of the mother, folic acid use and alcohol intake.

The researchers are explicit in their report that they do not know the cause of the elevated risks. 'Our findings could have been because of underlying infertility, small (sample) numbers or chance,' they said. Dr James Grifo, director of the fertility clinic at New York University Medical Center, US, agrees. He feels that due to the small sample size (281 assisted reproduction babies, 14,095 babies conceived naturally) more research is needed to confirm the findings. He also said that if the association with birth defects was real, the underlying cause was more likely related to the patients' infertility than to the treatments they had undergone.

'Any couple who is considering these treatments wants to be aware of all the pros and cons of the treatment,' Dr Reefhuis said, adding 'I think it's important for couples to be aware that there may be some increased risk for birth defects as well.' Professor Michael Chapman, a senior fertility specialist with IVF Australia, said 'There's no question that the evidence shows a slight increase, and responsible IVF doctors are saying that to their patients. But if your only way forward is IVF, then an increase in risk from one in 100 to two in 100 for most people is an acceptable risk.'