A report printed in the British Medical Journal this week about the trends in fecundity over time has called for more studies into the environmental factors contributing to reduced fertility rates.
Infertility is a common problem in affluent societies, affecting around 15 per cent of couples trying to conceive. In some rich countries, up to six per cent of children are conceived using assisted reproductive techniques.
Professor Jens Peter Ellekilde Bonde, a professor of occupational medicine at Aarhus University Hospital in Denmark, and Professor Jorn Olsen, a professor of epidemiology at the University of California, wrote the editorial. They explain that fertility rates are determined by biological, behavioural and social factors. These include sexual behaviour, desire for a family of a certain size, social conditions, and the age at which couples start their families. These cultural and social norms 'may mask more subtle biological changes in the population', they say.
With the advent of assisted reproductive techniques, the scientists say, 'subfertile couples may have as many children as fertile couples, so that genetic factors linked to infertility will become more prevalent in the generations to come'. They say that more direct markers of fecundity are urgently needed, and the best way to deal with the problem of infertility is to start with the avoidable causes of subfertility, such as obesity. The report has caused widespread worries in the media that IVF is 'creating an infertility timebomb'.
The call for more research into infertility is backed by Susan Seenan of the patient support group Infertility Network UK. She says: 'Infertility is an extremely distressing illness. Any research which helps must be encouraged'.