The birth rate among women in their early thirties has eclipsed that of women in their late twenties for the first time.
More babies are now born to thirtysomething mothers than any other age group, according to the Office for National Statistics (ONS). The birth rate is also increasing fastest among women in their late thirties and early forties, as more people put off becoming parents until later in life.
After hitting an all-time low in 2001, the birth rate has been steadily climbing for the past three years.
Last year, 639,721 babies were born in England and Wales, an increase of 2.9 per cent on 2003.
Women aged 30 to 34 had the highest birth rate, with 99.4 live births per 1,000 of the female population in that age group. In comparison, the live birth rate among women aged 25 to 29 was 98.5 per 1,000, falling to 72.7 per 1,000 among those aged 20 to 24. The average age of women giving birth is 29.6 years, compared with 26 in 1966.
Belinda Phipps, chief executive of the National Childbirth Trust, said: "We are certainly seeing more older women in our classes and groups who are in their thirties and forties.
"I think it is partly to do with education - many women now see themselves as having a career rather than just a job and want to spend time on a dual income and buying a house before starting a family.
"There are also a lot more role models out there which reinforces the idea that you can have children later.
"Years ago, the GP would be tutting if a woman was married and not pregnant by the time she was in her mid-twenties. Now it is seen as being perfectly acceptable to be having your first child in your mid-thirties."
While there were increases among all age groups, the ONS report highlighted the growing trend for women to wait even longer before starting a family. The biggest increase last year was seen among women over 40, where the birth rate increased by 6.1 per cent to 10.4 babies per 1,000 of their age group's population.
While some of these are women having their second or third baby, many are becoming mothers for the first time in their forties.
Some fertility experts are becoming concerned at the growing trend of women who are waiting so long before starting a family.
At a conference earlier this year in Copenhagen, Professor Michael de Swiet, of Queen Charlotte's Hospital in London, warned that soaring numbers of women in their mid to late forties were suffering ill health and complications in pregnancy because of the age at which they had conceived.
The ONS research also highlighted how the rising use of fertility treatment among women in their forties is contributing to an increase in the number of multiple births.
Last year, 9,294 women gave birth to twins, while 147 had triplets and five had quads - an overall rate which was 13 per cent higher than in 1994.
The multiple birth rate among women over 40 rose from 12 per 1,000 pregnancies in 1994 to 22 per 1,000 last year.
While fertility rates are now increasing, the trend for parenthood within marriage is on the wane. Last year, 42.2 per cent of births were outside marriage compared to less than a third 10 years ago.
However, more than two thirds of those births were registered jointly by parents who were living at the same address, with only 7 per cent of all birth registrations done solely in the mother's name.
Daniela Marenbach: 'At 32, I didn't feel I'd sacrificed myself at all'
Having a child in her early thirties rather than her twenties meant Daniela Marenbach, 33, didn't feel she had to sacrifice anything.
Daniela, who lives in Muswell Hill, north London, with her husband, Sean, and six-month-old Natasha, said: "When I had Natasha I was ready in terms of 'sacrificing myself for my child'. At that stage of my life I didn't feel I'd sacrificed myself at all."
Daniela, who married Sean, a software developer, when she was 29, said: "I had not envisaged getting married earlier than my late twenties. I saw my thirties as a time for family and children. I certainly wasn't ready for that in my twenties. I wanted to enjoy myself, travelling and working.
"I wanted to be able to give my full focus to my baby and reached a point financially where I knew I would be able to buy a house and have a happy standard of living."
Of the eight women in Daniela's National Childbirth Trust group, seven are aged between 32 and 35 and one is 40.
She said: "People are definitely marrying later in my peer group. Most of my friends haven't had children yet. I think we're more discerning about who we want to marry."
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