“A Concentration of Reproduction to Later Ages? A Worldwide Assessment of Trends in Fertility Timing,” a new paper in Population and Development Review, offers a compelling, data-driven exploration of one of the most profound shifts in modern demography—the increasing shift of childbearing to later ages.
This study draws on extensive global data, including United Nations World Population Prospects 2024 estimates and projections (covering 1950–2040), alongside historical records from the Human Fertility Collection and Database for select countries back to 1850. The authors examine “late fertility” (births at ages 30+) and “very late fertility” (ages 35+), measuring their absolute numbers, contributions to total fertility rate (TFR), and regional/national variations.
Global trends: A clear shift toward later childbearing
At the global level, the timing of births has changed markedly. Despite a decline in total global births—from 143.5 million in 1990 to 132.1 million in 2023—the number of births to women aged 30+ rose sharply from 35.6 million to 47.8 million over the same period. Today, more than one in three births (about 36%) occurred to women 30+, up from one in four (25%) in 1990.
Projections suggest this share will climb further in the coming decades. This trend reflects broader shift, driven by factors like education, career priorities, economic uncertainty, and evolving family norms.
However, the global figure masks stark regional disparities:
- In high-income regions (Europe, Northern America, Australia/New Zealand), nearly 60% of all births now occur to women 30+, with very late births (35+) rising notably.
- Eastern and South-Eastern Asia shows similar increases, often alongside ultra-low TFR.
- In contrast, Central and Southern Asia (29%) and sub-Saharan Africa (33%) maintain earlier patterns, even as overall fertility declines. Some regions, like South-Eastern Asia and parts of Latin America, exhibit stable late fertility shares despite sharp TFR drops, challenging assumptions of a universal link between low fertility and postponement.
The relationship between fertility levels and timing
A key distinction in our analysis is between late fertility (births at age 30 and above) and very late fertility (births at age 35 and above). While the share of births occurring after age 30 rises as fertility declines, births at ages 35 and above follow a different pattern.
But the relationship isn’t linear. At intermediate TFR levels (common in Latin America, Northern Africa, parts of Asia), late fertility sometimes dips first (as reproduction compresses into younger ages during early transition phases) before rising again at very low levels.
In low-fertility societies, childbearing increasingly concentrates in the early thirties, rather than shifting uniformly to ever-later ages. Even where most births now occur after age 30, births at ages 35 and above often represent a smaller share of late fertility than in high-fertility settings.
The result is a compression of reproduction into a narrower age window, rather than an unlimited extension of childbearing into later life. This pattern has important implications for reproductive health, the demand for assisted reproductive technologies, and the limits of fertility recovery through postponement alone.
Historical perspective: Not entirely new
A key insight comes from long-term European data (11 countries, 1850 onward). Late fertility followed a U-shaped trajectory: High in the 19th century (often >60% in Scandinavia), declining mid-20th century (demographic transition compressed childbearing to early 20s), then resurging since the 1980s.
Contemporary levels in Europe (55–70% at 30+) mirror or fall below some historical highs. This challenges views of childbearing shifts to later ages as purely modern—pre-industrial societies often had extended reproductive careers. Similar patterns appear in the US and Japan, but rapid fertility declines elsewhere (e.g., Iran, Vietnam, Thailand) show limited or delayed shifts to later timing.
Biological factors (e.g., later menopause in some populations) and social ones (e.g., intergenerational support, health access) can help explain variations.
Implications and conclusion
The concentration of reproduction to later ages is largely a phenomenon of developed regions (Europe, Northern America, Australia/New Zealand, Eastern Asia), coinciding with ultra-low fertility. Elsewhere, earlier patterns persist despite fertility declines, highlighting cultural, institutional, and policy roles.
This shift raises concerns for maternal/child health, infertility treatment demand, and intergenerational support. Yet historical evidence suggests it’s partly a return to pre-transitional patterns, not wholly novel.
This study shows that the shift of childbearing to later ages is a multifaceted, regionally varied process shaped by socioeconomic and historical forces. In an era of declining global births and aging populations, these insights inform nuanced policies on family, health, and demographics.
About the Authors
Thomas Spoorenberg, United Nations Population Division, Demographic Analysis Section.
Vegard Skirbekk, Norwegian Institute of Public Health and University of Oslo