Just under 50% of women are waiting until they reach 30 to give birth, according to the latest figures from the Office for National Statistics.
In 2010, 48% of all infants born were to mothers aged 30 and over, up from 47% in 2009 and 46% in 2000.
The last time so many babies were born to women of this age was after the Second World War, in 1946.
The proportion of mothers under the age of 25 has fallen steadily since its peak in the early Seventies.
More top news
Hollywood heartthrob George Clooney will be seen planting a kiss on Dame Maggie Smith during his guest appearance on Downton Abbey.
Alibaba - have you heard of it, know the name or what it is, or care what it does? Because you might want to.
The Tonight programme investigates the tough reality of life for people with learning disabilities in this country.