Most women in England and Wales are childless before the age of 30, official figures show for the first time.
A report by the Office for National Statistics (ONS) found that 50.1% of women born in 1990 were childless by their 30th birthday.
It is the first time there have been more childless women than mothers under 30 since records began in 1920.
A third of women born in that decade had been childless by age 30, by comparison.
Women born in the 1940s were the most likely to have had at least one child by this stage (82%).
But there has been a long-term trend of choosing to have children later in life and reducing family size ever since, the ONS said.
The most common age for childbearing is now 31, according to ONS estimates based on the latest data, compared to 22 among baby boomers born in the late 1940s.
Figures from the Office for National Statistics (ONS) show that 53% of women born in 1991 had not had a child by their 30th birthday last year. The graph shows: The proportion of childless women at the age of 30 according to their date of birth
ONS data also shows the average number of children a woman has had by age 30 has fallen since 1971, when it stood at 1.89.
The proportion of women reaching 30 who are childless has risen steadily since the late 1970s, when around one-fifth were childless.
This proportion increased dramatically in the following decade. In 1980, 24% of women aged 30 were childless, rising to 37% in 1990.
At the turn of the century, some 43% of women had a child before their 30th birthday. And last year, it broke the 50% mark for the first time.
Amanda Sharfman, ONS statistician, said: “We continue to see a delay in childbearing, with women born in 1990 becoming the first cohort where half of women remain childless by their 30th birthday.”
“Infertility levels at age 30 have risen steadily since a low of 18% for women born in 1941.
“Lower fertility levels among people currently in their twenties indicate that this trend is likely to continue.”
At the same time, the number of women who never have children has increased.
The report found that 18% of women aged 45 will be childless by 2020.
Modern women of all ages are also choosing to have smaller families.
Mothers have, on average, 1.92 children now, which is lower than the 2.08 for their mothers’ generation.
Families with two children remain the most common family size (37%), but this is a decrease in the proportion of those with two children compared to their mother’s generation born in 1949 (44% ).
Ms Sharfman said: “The average number of children born to a woman is less than two for women born since the late 1950s.
“While families with two children are still the most common, women who have recently finished childbearing are more likely than their mothers’ generation to have only one child or none at all.”
The ONS said: “While average family size has fallen, families with two children remain the most common family size for both generations, with 37% of women born in 1975 and 44% of those born in 1949 having two children.
“Among people born in 1975, 27% had three or more children and 17% had only one child, compared to 30% and 13% respectively for their mothers’ generation.
