Fertility rates for women under 30 in England dropped to their lowest levels since 1938, new figures revealed.
Low levels, not seen since the 1980s, were also recorded for Wales, the Office for National Statistics (ONS) said.
The total fertility rate for the two countries fell from 1.7 children per woman in 2018 to 1.65 children per woman in 2019.
Those aged 40 and over were the only age group to see an increase in the fertility rate, with a rise to 16.5 births per 1,000 women.
The total fertility rate is worked out by calculating the average number of live children a mother would have while she is of childbearing age, if she experienced the typical fertility rate every year.
The rates were measured in six age groups, from under 20 up to 40 and over.
The ONS suggested possible reasons for the decrease in total fertility rates could be better access to contraception, a fall in mortality rates of children aged under five (resulting in women having fewer babies) and lower levels of fertility or difficulties conceiving because people are delaying having children until later in life.
Last year the standardised mean age of a mother at childbirth was 30.7 years, a figure which has been gradually rising since 1973 when it was 26.4 years.
The statistics, published on Wednesday, also show a continued decrease in live births, with 640,370 in England and Wales in 2019.
This is a fall of 2.5 per cent since 2018 and a 12.2 per cent decrease since the most recent peak in 2012.
Last year more than a quarter (28.7 per cent) of live births were to women born outside the UK – a record high since 1969, but continuing a general long-term increase, the ONS said.
Poland remained the most common country of birth for mothers born outside the UK, while Pakistan remained the most popular country for fathers.
While England’s stillbirth rate fell to a record low for the third year in a row to 3.8 stillbirths per 1,000 total births, the rate in Wales rose from 4.4 to 4.6 stillbirths per 1,000 total births in 2019.
David Corps, from the vital statistics outputs branch of the ONS, said the rate in England must fall further to 2.6 by 2025 to meet a Government aim to halve stillbirth rates in the country by then.
“The story of births in England and Wales in 2019 is one of decreases and record lows, with the total number of births continuing the fall we’ve seen in recent years,” he said.
“Wales had the lowest fertility rate since our records began and England’s is nearing its record low.
“For stillbirths, the rate in England continued the decline seen in recent years, reaching a record low of 3.8 stillbirths per 1,000 total births in 2019.
“To achieve the government ambition to halve stillbirth rates in England by 2025, the rate must fall to 2.6 by that year.”
Clare Murphy, from the British Pregnancy Advisory Service, said: “In many ways these figures tell a story of success.
“The increasing age of motherhood is a reflection of improved gender parity, especially greater female participation in both higher education and the workplace.”
But she said financial factors also “weigh heavily on family planning decisions”.
She added: “The job market has never been more precarious, and we know the current crisis has hit women’s employment particularly hard.
“As a result, we may well see these trends continue into the future as women and couples choose to delay having children until they are financially stable.”
