Couples trying for a baby were told yesterday that doctors' usual measure of clinical infertility - no pregnancy after a year - was unsound. Instead, a new study showed that most healthy couples who keep trying for two years would conceive, even if they were in their late 30s.
One implication of the study, led by David Dunson of the National Institute of Environmental Health Sciences in North Carolina, is that couples are being hustled into the expense and risk of fertility treatment, like IVF, too soon.
Dr Dunson said that if there was no clear medical reason for the delay in conceiving, it was better to wait. "Many couples are recommended for assisted reproduction therapy because of known reproductive problems, but often just because they haven't been able to conceive after a year. In these cases, doctors might be overly hasty in recommending couples for treatment."
Although the research was done in the US, it used data from seven European cities, including London. It found that even when the women were aged between 35 and 39, fewer than one in 10 failed to conceive after two years unless the male partner was over 40.
It was Dr Dunson's research earlier this year which showed that fertility in women started to decline as early as the late 20s for women, and the late 30s for men. But this research referred to the chances of getting pregnant on a month by month basis.
The new study underlines the fact that while older couples may take longer to conceive naturally, they still had a very good chance if they gave it those extra months.
Almost two fifths of women aged 35 to 39 failed to conceive within a year, compared to only 8% of 19- to 26-year-olds. But if the older group gave it another year, the number failing to conceive was halved. In the younger group, after two years, 3% were unsuccessful.
"There is a large amount of normal variability in fertility and many couples having below average but normal fertility may fail to conceive within a year," said Dr Dunson. "This is particularly true for older couples, many of whom fail to conceive within the first year but are successful in the second."
In Britain, GPs start making referrals for medical tests and fertility treatment when a couple has been trying for a child after a year.
If a couple ended up having IVF treatment, it was difficult to get the NHS to pay for it, and each cycle cost several thousand pounds. IVF involved injections for the woman, was more likely than not to fail first time, and carries risks.
"Fertility treatment such as IVF can result in an increased risk of multiple pregnancies, pregnancy complications, low birth weight, birth defects and long term disability among surviving infants. In addition, the chance of success ... decreases with age, while the side effects increase in prevalence," said Dr Dunson.
Increasingly, women are caught in a fertility squeeze, between the pressure to have children later for career reasons and earlier for biological reasons. Dr Dunson's research offers a message of hope.
"Clinical infertility after 12 months clearly increases with age, so couples can expect to take longer to conceive as they age," he said. "However, most women who don't conceive within 12 menstrual cycles conceive within the next 12.
Ulrik Kvist, professor of andrology at the Karolinska Institute in Sweden, endorsed Dr Dunson's findings, but suggested another approach - that couples who had trouble conceiving after six months should be checked for problems like low sperm count or non-ovulation. If they were clear, it should be suggested they keep trying naturally until the two-year point had been reached.
