Babies born after in vitro fertilisation (IVF) are three times more likely to develop neurological disorders including cerebral palsy than children conceived naturally, a study has found.
Scientists believe the findings could be explained by the complications that often arise when two or more IVF embryos share the same womb, rather than because of the IVF techniques themselves.
Although the study did not rule out the possibility that fertilising human eggs in a test tube might in itself be implicated in developmental problems, it did not find any statistically significant evidence to prove this.
Bo Stromberg, who led the investigation at the University Children's Hospital in Uppsala, Sweden, said the findings supported the view that only one IVF embryo should be implanted into a woman rather than the two or more routinely used in many countries including Britain.
"We think that IVF is a good treatment and a vital option for couples who can't have babies naturally, but we have to think of a baby's future life, and not just that of the couple," Dr Stromberg said. "I think we should decrease the number of eggs implanted, to one at a time. Isee it as the baby's right to have a healthy life."
The study, which used Sweden's extensive health records, compared 5,680 IVF children aged between 18 months and 14 years with 11,360 youngsters of the same age who were conceived naturally.
Dr Stromberg also compared twin births with single births. IVF in Sweden produces a relatively high number of twins because two embryos are routinely implanted into patients to raise the chances of a successful pregnancy.
The scientists say in their report published in The Lancet: "Our findings show that children born after IVF have an increased risk of needing treatment in a childhood disability centre. Our results can largely be, though not solely, explained by the high frequency of twins born, and by low birthweight and low gestational age, but an effect on the IVF procedure per se or other factors not adjusted for cannot be excluded."
Twenty-three years have passed since the first test-tube baby was born. Worldwide, there are about 50,000 IVF children born a year, yet next to nothing is known of any possible long-term effects on their health.
The Swedish study was not big enough to discern any inherent problems with the IVF techniques used, such as the direct injection of a single sperm into an unfertilised egg, or the effects of inducing the production of eggs in a woman.
Dr Stromberg also found an increased risk of cerebral palsy in children resulting from single IVF pregnancies but, unlike in IVF twins, this was not statistically significant.
David Healy and Kerryn Saunders from Monash University in Melbourne, Australia, write in an accompanying article that this is a puzzling finding, but say the precise causes of cerebral palsy remain unknown. "The study by Stromberg and colleagues is valuable, but does not remove the need for clinical studies. It certainly heightened the need for a shift from multiple to single-embryo transfer," they say.
Two or three children in every 1,000 suffer from cerebral palsy and the higher-than-average proportion of IVF children with the disorder might also be explained if infertility itself is a risk factor, they say.Reuse content