KEY POINTS:
Sarah North has decided to have a newly available fertility test to see if she should start having babies straight away.
Miss North, a 31-year-old pharmaceutical company representative who lives with her partner at Laingholm in West Auckland, is certain she wants children - two, three, possibly even
four.
But she also has a mortgage. So, like many women around her age, she is weighing the benefits of delaying childbearing - such as greater financial security - against the risk that if she waits too long she might need IVF fertility treatment or not be physically able to have them at all.
"Ideally I picture myself at about 35 having children rather than right at this minute."
But how long can she wait?
The blood test she plans to have next week should give her an idea. A check of her level of an ovarian hormone called anti-Mullerian will show how many eggs she has left, a predictor of her chances of becoming pregnant.
The new test - more sensitive than the existing method, which checks the level of follicle stimulating hormone - has been available overseas for several years. Now two chains of private fertility clinics in New Zealand have started offering it: Repromed, at a cost of $85, and Fertility Associates, at $45-$50.
A woman's number of eggs is set at birth and declines naturally during her life. Egg quality also starts declining, then this accelerates in the 30s. Both factors affect fertility, which is at its peak around the age of 28.
In the mid-20s, it takes on average three months to become pregnant, rising to six months in the mid-30s and a year at 40.
At least 10 per cent of women in their early 30s have an abnormally depleted reserve of eggs, but most do not know.
The existing test can reveal this abnormal depletion only once the quality of the eggs has deteriorated significantly.
The new test can also help to predict the risk of miscarriage and to tailor the dose of fertility drugs in IVF, but Fertility Associates director Dr Richard Fisher expects its main use will be to help women with a reduced egg count for their age decide when to try to start a family.
Repromed Auckland's medical director, Dr Guy Gudex, said he often saw couples who had been together for many years who, had they known they were going to have difficulty conceiving, would have started trying sooner.
"Just a couple of years can make all the difference."
If a woman's anti-Mullerian hormone level was low, "we might encourage a couple to plan their family earlier."
* The test
A blood test to measure the level of an ovarian hormone called anti-Mullerian.
It helps assess a woman's biological clock - fertility of ovaries' remaining eggs - better than existing test.
Can predict risk of miscarriage.
Also helps choose correct dose of fertility drugs, avoiding hyper-stimulation of the ovaries, a potentially fatal syndrome.
Cost: $45 or $85, depending on clinic.
