The number of women giving birth past their 30th birthday has risen by more than half in the past two decades.
Figures show that increasing numbers are delaying motherhood, with many getting pregnant in their forties.
But while the overall number of conceptions is still on the rise fewer are having babies in their teens or twenties.
Experts say the data from the Office for National Statistics show that many women are choosing to wait before starting a family as their career and life opportunities have improved, and that better healthcare and fertility treatment is making it easier to become an older mother.
Elizabeth Duff, a senior policy adviser at the Natural Childbirth Trust, said: “The rising numbers of women conceiving for the first time in their 30s or 40s follows a trend we have seen over the past decade, although the number conceiving over 40 is still relatively small. Many older women who are fit and well can go on to have a straightforward pregnancy and birth, and a healthy baby.
“There are many reasons women may choose to become a parent later on in life, including a desire to build a career or achieve financial independence, or that they don’t feel ready to settle down. Older women should feel well supported and confident in being able to give birth and have the type of birth they want and maternity services should be equipped to help meet these needs.”
Anastasia de Waal, Head of Family and Education at the think-tank Civitas, said: “The latest ONS figures indicate that right across the board the age of first pregnancy is getting later.
“Whilst childbearing used to start in our twenties, today women are increasingly waiting until their thirties.
“This postponement is largely to do with women’s far greater involvement in the labour force. For middle and upper-income background women in particular, babies now frequently follow a decade of higher education and career development.
“Another key contributor to current childbearing trends is that many couples feel unable to cope with the cost of raising a child until they have reached a higher earning capacity.”