Women will soon be able to tell how many eggs they have in their ovaries in a simple hormone test that Australian researchers say could revolutionize family planning and fertility treatment.

The so called "egg timer" blood test would be able to accurately predict ovum levels based on the concentration of a specific fertility hormone, said conception specialist Peter Illingworth.

"I think this is a big step forward," said Illingworth, medical director of IVF Australia.

"What the test will do is identify those younger women who may well be at serious risk of not having children easily when they're older," he told public broadcaster ABC.

"It will identify women who are at risk of having a premature menopause, for example, and allow women to plan how active they should be about fertility treatment."

Women who had undergone treatment for cancer or endometriosis or had ovarian surgery would particularly benefit from the anti-mullerian hormone (AMH) test, he said, which would cost just $58.

It could also save couples tens of thousands of dollars in expensive but ultimately futile in-vitro fertilization (IVF) treatments, Illingworth added.

Women are born with an average of one to two million eggs in their ovaries, which are shed monthly until menopause, with a 20-year old woman typically having 200,000 eggs.

That number halves as she enters her 30s and dwindles to as low as 2,000 after the age of 40.

Copyright AFP