Women will be urged to work out a reproductive life plan from the age of 25 to prevent the agony of not being able to have children.
Fertility experts say not only does a woman's chance of having a baby decline with age but her risk of breast and ovarian cancers increases the longer childbirth is delayed.
The Garvan Institute of Medical Research is targeting professional Sydney women aged between 25 and 35, warning that maintaining a healthy lifestyle is not enough to preserve fertility, and IVF cannot be considered a fail-safe back-up plan.
Newtown gynaecologist Gabrielle Dezarnaulds said women have a fixed number of eggs to last them a lifetime and fertility drops sharply from the late 30s as the number and quality of eggs dwindle.
Success rates for assisted reproductive technology also decline the longer a woman's biological clock has been ticking, she said.
"I'm not saying you should get pregnant before a set age, but go and chat to your GP, even if you're not aiming to get pregnant immediately. Work out a time frame when you might start to, and if you are ready to have a baby, get on with it."
Dr Dezarnaulds said hormone tests and ultrasounds can give some indication of the number of eggs a woman has, but "your eggs are as old as you are and there's nothing you can do to stop their ageing".
Soon, she said, young women may be able to freeze their eggs for use later in life, but thawing them had proved largely unsuccessful because ice crystals form inside the egg and damage genetic material.
Some fertility clinics, including Sydney IVF, have introduced vitrification, a very fast cooling technique that stops the formation of ice crystals. The technique had been offered only to women with such medical conditions as Turner's syndrome and those who had undergone chemotherapy, but now it is available to anyone, even young women who want to store their eggs, for about $15,000.
The Garvan Institute's head of ovarian cancer research, Philippa O'Brien, said delaying childbirth increased not only the risk of infertility but also the risk of developing breast and ovarian cancers.
One in eight women will be diagnosed with breast cancer and one in 67 with ovarian cancer before they turn 85. Dr O'Brien said women with a family history of the diseases needed to be more aware of the risks.
Rebecca Biggins, of Mona Vale, had her first baby, Abbey, 1, when she was 25 because she didn't want to risk having any troubles conceiving.
"My mum was 37 when she had my brother and 39 when she had me and she had problems and I don't want to go through that," she said.
"I never wanted a high-profile career but I always wanted to be a mum, so that was my priority."
The Garvan Institute will host the forum "Age And Fertility: How Late Can I Wait?" with MC Andrew O'Keefe on Thursday night.
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