The fertility rate has hit its highest level since 1980 as more women in their late 30s and 40s have babies, official figures show.
Fertility rates have been rising for five years
The Office for National Statistics data revealed women are having 1.87 children on average - up from 1.8 in 2005.
The fertility rate in England and Wales has been rising since the all-time low in 2001 of 1.63 following an almost continuous fall since the late 1980s.
But experts predicted it was unlikely to keep rising.
The upturn has been largely driven by increasing birth rates among older women.
The highest percentage increase for any age group was for women from 35 to 39 which rose by 7% in a year.
Fertility rates have also doubled for women aged 40 and over in the last 20 years.
Professor Danny Dorling, an expert in human geography at Sheffield University, said the changes in recent years were being driven by the change in university admissions during the 1980s.
"In that period many more women started to go to university which meant that they ended up delaying having children.
"I believe the fall that we have seen was due to this group and what is happening now is that these women are now having children but at a later age than they once did.
"We are not likely to get to the replacement level - two children per woman - but that is not necessarily a concern because immigration is making up for that."
Dr Richard Kennedy, of the British Fertility Society, said the trend represented a challenge to health professionals.
He said experts would advise women not to delay having children for too long, but said it would be "unrealistic" to expect a change in behaviour.
While the total fertility rate is at its highest for 26 years, it is still well short of the figure during the 1960s which stayed well above two children per woman.
The all-time high was recorded in 1964 when it hit 2.93.
In total, there were 669,531 births in 2006 with over a fifth of them to mothers born outside the UK - a figure which is also rising.