London: Thousands of women who take high doses of fertility drugs as part of in-vitro fertilisation (IVF) treatment are actually harming their chances of ever having a baby, doctors are warning.

Increasing reliance on such powerful drugs may be preventing women from getting pregnant and damaging their eggs, new studies suggest.

A conference of fertility experts this month will call on the IVF industry to rethink its approach. The hormones used to "kickstart" the ovaries could cause chromosomal damage to more than half of eggs, rendering them useless. The treatments may also affect the womb lining, preventing embryos from implanting.

However, women who have failed previous IVF attempts may be able to improve their chances of conception by reducing the dose of fertility drugs.

Growing concern over the potentially damaging effects of such drugs will be discussed by fertility experts, including the "father" of IVF, Professor Bob Edwards, at the first annual meeting of the International Society of Natural Cycle Assisted Reproduction (ISNAR) in London in a fortnight.

Professor Edwards helped to create the world's first test-tube baby, Louise Brown, in 1978, using natural cycle IVF, in which egg collection is timed to coincide with ovulation, rather than drug-induced production of a large number of eggs.

Other specialists are calling for minimal-dose drug regimes to be used gleaning fewer eggs but which may have more chance of producing a baby.