A genetic test that can tell a woman how long she has left to start a family might be on offer by the next year, say scientists.

Researchers have claimed that by 2010, a new test would be on the horizon, which could detect the presence of a gene that seems to predict the rate at which a woman's egg supply diminishes.

The test is aimed to tell a woman in her early 20s whether she is at high risk of early menopause. If she is, monitoring her egg supply will confirm whether her fertility is in early decline.

With this information, a woman could then decide whether to start a family sooner or later, or freeze some eggs to increase her chances of conceiving later on.

A woman is born with all the eggs she will ever have- 1 to 2 million immature eggs or follicles- out of which 400 will mature and could be fertilised during her reproductive life.

By puberty, a girl has around 400,000 follicles left, and this continues to decline until menopause, when only a few hundred remain.

The number of follicles a woman has left at any time in her life - her "ovarian reserve" - approximately reflects how many eggs she will release.

After 35, most women experience a sharp drop in their ovarian reserve, and thus their fertility, but around 10 per cent of women experience "early ovarian ageing" in their 20s.

Norbert Gleicher of the Center for Human Reproduction in New York has claimed that the new test could predict early ovarian ageing before it happens, using a gene already implicated in reproductive ageing.

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