The number of women giving birth in their 40s has TREBLED in 20 years – because women are delaying motherhood to build their careers.
Many also said it had taken that long to find the right partner. Older mums had 29,250 babies last year - compared with 9,835 in 1991.
While most women say becoming an older mum gives them a new lease of life, experts warn that the trend is not ideal.
Older mums-to-be carry more risk of complications, Charles Kingsland, consultant gynaecologist at Liverpool Women's Hospital, told BBC Breakfast.
"You are born with all your eggs and as you get older, the eggs get older with you, which causes a reduction in quality," he said.
"Ideally, a woman would have children in her 20s, but unfortunately we don't live in an ideal world."
Last year the number aged 35 to 39 who gave birth was 3.4 per cent higher than in 2010, according to the Office for National Statistics.
The remarkable rise in older mums has been partly made possible by IVF, donor eggs and other fertility treatments.
But many gave birth naturally, including TV star Amanda Holden and actress Nicole Kidman - both in their early 40s.
There are benefits of being an older mum.
Research by the Royal College of Paediatrics and Child Health showed that kids born to older mums were more likely to be high achievers at school.
However, writer and mum-of-four Joanna Moorhead, who is now in her 50s, told the BBC she was worried about the trend continuing.
"I had my first child when I was 29, which was much older than when my mother had me," she said.
"Will my daughter have her first baby when she is much older than when I had mine?"
She said she hoped role models like Adele would help to reverse the trend. The superstar singer is expecting her first child at 24.
"There is a herd instinct about people having children," Joanna said.
How old were you when you had your first baby?
Do you think there's such a thing as an ideal age for both your body and your career?