Most babies in Britain now born to women in their early thirties

The most popular age to have a baby has passed 30 for the first time. Increasing numbers of women are putting off having a family until they have established relationships and settled careers, figures show.

In every age group under 30 the birth rate is falling, but in every age group over 30 it is rising, the statistics from the Office of Health Economics (OHE) show. The fastest rise has been in births to women over 45, a 50 per cent increase from 2000 to 2005.

Doctors have warned that modern career women who delay starting a family until into their 30s are defying nature and risking heartbreak because older women have an increased chance of suffering health problems, ranging from high blood pressure to diabetes and birth defects.

Among those aged 30 to 34, the live-birth rate in 2005 was 100.5 per 1,000 women, the highest for any age group and a 13 per cent increase since 1995. For those aged 25 to 29, it was 98.1 per 1,000, a 10 per cent decline in that period.

Mary Newburn, head of policy at the National Childbirth Trust, said women were better educated, had better career prospects and were earning more than in the past. They also wanted the same opportunities and freedom as men. "They have a lot of freedom and a lot to lose by settling down," she said. "The cost of housing has risen and all the rites of passage - getting married, buying a home and having a baby - are moving later. Women are enjoying earning and their freedom to travel."

The age of first motherhood has been rising since the 1970s, with the sharpest increases being in the late 30s and early 40s. But the "biologically optimal" time for childbearing is 20 to 30.

The trend to later motherhood is fuelling a rise in Caesareans. Almost one in four births in 2004-05 was by this method and the rate is continuing to rise, the OHE said. The greater demand has been blamed on women who demand the operation to plan births that fit in with busy lifestyles. But the figures do not bear this out. Only 7 per cent of Caesareans are at the mother's request, according to doctors. There was a small drop in "elective" [planned] Caesareans in 2004-05 with the increase driven by a rise in emergency ones.

The ageing of Britain's mothers is one factor behind the increase. The risk of a Caesarean rises sharply with age. Increasing obesity and the growing incidence of twin and triplet births after IVF treatment are also fuelling the rise in Caesareans. The World Health Organisation said 20 years ago there was no justification for a rate higher than 15 per cent, but many countries have ignored its advice. The Caesarean rate is 26 per cent in Germany, 29 per cent in the US and 37 per cent in Italy. But it is only 13.6 per cent in the Netherlands. Ms Newburn said: "Caesarean rates are high in Catholic countries with paternalistic medical systems and low in those with strong midwife-led maternity services."

Overall the birth rate has been rising since 2002 when it hit an all-time low of 669,000 births. In 2005 there were 722,000.

But the fertility rate is still too low to achieve "replacement" level - sufficient to maintain the population at its present size. Unless fertility rates increase, or immigration is encouraged, the population of Britain, in common with many other European countries, will fall in the next few decades.

'I wanted to do it the right way. Then it just happened' Caroline Mizen, 42

Caroline Mizen wanted to wait until she was married to have children. She was 34 when she gave birth to Francesca, now nine, and had Jack, now seven, three years later. Mrs Mizen had two miscarriages which she says reinforced her desire to have children. "I wanted to do it the way I saw as the right way. I wasn't mature enough and hadn't met the right person.I don't know if we consciously decided we wanted children, it just happened". Mrs Mizen now works as a pre-school carer in Billericay, Essex.

Sara Newman

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