Official figures for England and Wales show the number last year was 48 percent, up from 46 percent 10 years ago, the Daily Express reported.
The average age of all women giving birth is also up from 28.5 in 2000 to 29.5 and the average at which women have a first child has risen from 26.5 to 27.8 years.
The statistics indicate that the women are postponing childbearing while they concentrate on a career or try to get on the property ladder. A fifth of babies were born last year to women over 35.
"People are under economic pressure, they have heavy costs and debts, they delay having children and their biological clocks tick on. Those that have children late feel great while they are in their 30s and 40s but 15 years on they may not be so healthy," said Patricia Morgan, a sociologist.
The study found that the births by single mothers had also risen from 43 percent in 2005 to 47 percent.
Seventeen girls aged 13 or younger gave birth in 2010 as did 183 14-year-olds, the British study found.