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
Trials of a new prenatal test for Down's Syndrome have been launched to see if it should be offered to women on the NHS
Zayn Malik has spoken for the first time since quitting 1D saying he was upset to let fans down but that it wasn't "real" to him anymore
Coronation Street actress Samia Ghadie has announced she is expecting her first child with ice dancer Sylvain Longchambon.