Worldwide, the path leading to delayed fertility is more complex than it may appear at first sight. Thomas Spoorenberg and Vegard Skirbekk offer a few keys to better interpret current trends.
Across the world, the timing of childbearing is changing rapidly. In 2023, more than one in three births occurred to women aged 30 or older, up from one in four in 1990. Using data from the World Population Prospects 2024 and long-term historical fertility series, it is possible to follow the evolution of late (ages 30+) and very late (ages 35+) fertility from 1950 to 2040 worldwide, for 11 countries since 1850 (Spoorenberg and Skirbekk 2025). It emerges that the recent concentration of fertility to later ages is primarily a feature of developed regions (Europe, Northern America, Australia and New Zealand, and Eastern Asia) while in much of the developing world, the timing of reproduction remains relatively stable, even amid fertility decline.
Late fertility is rising globally, but unevenly
Globally, total births declined from 143 million in 1990 to 132 million in 2023. Yet births to women aged 30 or older increased from 36 to nearly 48 million. Among them, births at ages 35 and above rose from 14 to 20 million, now representing over 40% of all late births.
Overall increase masks striking regional disparities. In Europe, Northern America, Australia, and New Zealand, 57% of all births in 2023 occurred to women aged 30 or older, up from 29% in 1990. Eastern Asia shows similar trends, with late fertility rising from 19% to 44%. These regions have experienced a pronounced shift toward later childbearing coinciding with ultra-low fertility levels.
In contrast, many developing regions maintain earlier childbearing patterns despite significant fertility declines. Central and Southern Asia recorded only 29% of births after age 30 in 2023, while sub-Saharan Africa remained stable at 33%. Remarkably, South-Eastern Asia shows stable timing patterns despite total fertility declining from well above replacement in 1950 to below replacement today. In short, fertility postponement is not a universal correlate of fertility decline.
The link between fertility decline and late fertility
The relationship between total fertility and late fertility is clear but non-linear (figure 1).
In high-fertility contexts such as sub-Saharan Africa, late fertility contributes about 35-45% of total fertility. During early stages of the fertility transition, reproduction tends to be compressed into younger ages. Only at very low fertility levels does childbearing become strongly concentrated at older ages, with 60% or more of births occurring after age 30, driving late fertility upward again. This pattern indicates that fertility postponement emerges primarily in advanced stages of demographic transition, when small family norms combine with delayed marriage, prolonged education, and economic uncertainty.
“Very late” fertility follows a different trajectory
While late fertility rises as overall fertility declines, very late fertility (ages 35+) does not follow the same trajectory. In 2023, very late births accounted for 42% of late fertility worldwide, down from over 50% in the early 1970s, with births now increasingly concentrated in the early 30s.
In high-fertility settings like sub-Saharan Africa, 50-60% of late births occur at ages 35+, reflecting extended reproductive careers, while in low-fertility Europe and Eastern Asia, this share drops to 35-45%. This narrowing reproductive window heightens the biological and social pressures of delayed parenthood and increases demand for fertility support services.
Historical perspective: not entirely new
Historical data for 11 countries reveal that today’s levels of late fertility are not unprecedented (figure 2). In European countries, during the 19th century, births at ages 35+ often constituted over 50% of late fertility, reflecting extended reproductive careers in pre-transitional regimes. Sweden and Norway maintained late fertility shares above 60% throughout much of the 1800s, levels only now being approached again.
This reveals a distinctive U-shaped trajectory: high late fertility in pre-industrial periods, decline during the mid-20th century demographic transition, and resurgence since the 1980s.
Contemporary fertility postponement in Europe represents not an entirely new phenomenon but a return to pre-transitional reproductive patterns, though under very different circumstances. Historically, late fertility reflected continued childbearing within large families; today, it reflects delayed entry into parenthood and smaller completed family sizes. The current rise in very late fertility, however, exceeds historical levels in most countries, enabled partly by medical advances and assisted reproductive technologies.
Implications and outlook
The shift of reproduction to later ages represents one of the most consequential demographic transformations observed since the late 20th century, affecting fertility rates, population ageing, maternal and child health, and intergenerational transfers.
Yet this shift is far from uniform. As low fertility spreads globally, monitoring whether other regions will replicate the European trajectory becomes crucial. In countries like Iran, Vietnam, and Thailand, which experienced rapid fertility declines to below-replacement levels, late fertility shares have remained relatively stable or increased only modestly, contrasting sharply with European patterns.
Understanding these divergent pathways is essential for projecting future demographic trends and developing appropriate health, social, and demographic policies. Policymakers should anticipate the reproductive health implications of postponed childbearing, especially the growing need for fertility support and maternal care at older ages.
Reference
Spoorenberg, Th. and Skirbekk V. 2025. “A concentration of reproduction to later ages? A worldwide assessment of trends in fertility timing.” Population and Development Review Online First Article. http://doi.org/10.1111/padr.70036