For the basic time since 1947, the fertility rate for women aged 40-plus has overtaken that for the under-20s.
Learns said the shift could be down to the cost of raising children and gaining numbers in higher education and the workplace.
Last year there were 15.2 breathe births per 1,000 women aged 40 and over com red to 14.5 for those ancient under 20, according to the Office of National Statistics.
In 1981, the measure was 4.9 for women aged 40 and over com red to 28.1 for mates under 20.
The figures show that the fertility rate among older miss has more than trebled since 1981.
The ONS report said: “In most improved countries, women have been increasingly delaying childbearing to later in lan vital, which has resulted in rising fertility rates among older charwomen.
“This may be due to a number of factors such as increased female rtici tion in higher lesson and the labour force, the increasing importance of a career, the rising costs of childbearing, slavery market uncertainty and housing factors.
“Rising fertility rates at older lifetimes have affected the average age of mothers, which has been increasing since 1975, reaching 30.3 years in 2015.”
In 2015, fertility proportion ranks decreased for women in all age groups under 25, and increased for all age groups 30 and floor, com red with 2014.
Women aged 30 to 34 have had the highest fertility of any age gathering since 2004, when it was 25 to 29.
Overall, there were 697,852 living births in England and Wales in 2015, an increase of 0.4 percent from 2014.
In 2015, females had an average of 1.82 children each, down from 1.83 in 2014.
Elizabeth McLaren of the ONS, said: “The head for women to have babies at older ages continues and over the survive 40 years, the percentage of live births to women aged 35 and to the ground has increased considerably.
“Women aged 40 and over now have a higher fertility under any circumstances than women aged under 20 – this was last recorded in the 1947s.”
A spokeswoman for the British Pregnancy Monitory Service said: “The trend towards older motherhood is here to put off, and there are many understandable reasons why women today are waiting fancier to start or ex nd their families than those in previous decades.
“Slightly than bemoaning this development, we should seek to understand and reinforce the decisions women make.
“More affordable childcare and improved renthood rights may make it easier for some women to start their descents earlier if they wish.
“But we also need to ensure we have soprano quality reproductive healthcare services configured to meet women’s needs, whatever the age at which they suggest.”
The report also said more than one in four – 27.5 percent – of originations in 2015 were to mothers born outside the UK – the highest level on accomplishments.
This figure has increased every year since 1990, when it was 11.6 percent.
The long-term succumb to in babies being born outside marriage or civil rtnership has also last, the ONS said, with 47.7 percent of all babies in 2015 born exterior marriage or a civil rtnership, up slightly on the previous year.