The pregnancy rate in women over 40 is rising faster than in any other age group. A total of 22,700 women over the age of 40 became pregnant in 2004, twice the number of 11,500 pregnancies in the age group in 1988.
The age at which women become pregnant for the first time has been rising since the mid-1970s, with the sharpest increases in births being found in women in their late thirties and early forties.
The trend has been for women to spend more time building their careers before starting a family. But doctors have warned that women who delay starting a family risk heartbreak. Fertility declines rapidly after 30 and older mothers face increased complications in pregnancy and labour.
Figures released yesterday show that among women aged 40 to 44 there were 11.3 conceptions per thousand women in 2004, 6 per cent up on the previous year and 74 per cent up on the rate in 1988.
The Office for National Statistics, which published the figures, said overall conceptions rose by 2.4 per cent in 2004, to 826,000. More than one-fifth ended in miscarriage or abortion.
In 2004, 55 per cent of pregnancies were outside marriage compared with 44 per cent a decade earlier.
Pregnancies among girls under 18 fell by 1.4 per cent in 2004 to its lowest level since 1995. But the cumulative drop of 11 per cent since 1998 fell short of the government target of a 15 per cent reduction by 2004.
The British Fertility Society issued a stark warning to women last year not to delay trying for children in the belief that they could fall back on in vitro fertilisation (IVF) if all else failed.
The society said women should not be lulled into a false sense of security by success stories of couples becoming parents late in life. Fertility clinics have reported a significant increase in older applicants.
Specialists say there is an increased risk of dying during childbirth for older mothers, rising from 7.3 per 100,000 births for women aged 20 to 24, to 35.5 per 100,000 for women over 40. Older mothers are also at increased risk of hypertension - high blood pressure which can lead to pre-eclampsia, a condition that can be fatal for mother and unborn child. There are also increased risks of miscarriage, chromosomal disorders such as Down syndrome, and diabetes.
Some experts have predicted that Britain faces a fertility time bomb over the next decade as women delay childbearing. As many as one in three couples may have difficulty getting pregnant if present trends continue.
Clare Brown, chief executive of Infertility Network UK, the charity that supports couples with fertility problems, said: "Delaying having a children is a choice many women make but they need to be aware of the problems."
Marion Frostick, 47: 'I've been very lucky. Others aren't'
After spending her 20s building her career in management, Marion Frostick tried to get pregnant in her early 30s. She found she could not conceive.
She spent the next 10 years trying. She went through years of tests and investigations, the stress of which contributed to the breakdown of her first marriage.
When she remarried, at the age of 36, she was still unable to get pregnant and finally resorted to IVF. She was successful first time and got pregnant again at her second attempt, aged 41.
"I have been very lucky, I know it doesn't work out for everybody. It is very hard for women - they have more choices. If you are driven and want an interesting career it means you have to make difficult decisions."
Now aged 47, she works as a management trainer, and lives with her husband and two children in Oxford. Warning women about the risks of late motherhood is right, she says, but some women don't have the choice.Reuse content