Delayed reproduction, i.e. people becoming parents at older ages, began as a major demographic trend in western Europe in the 1970s. Since then, it has become common in all high-income countries and many middle-income countries worldwide (Beaujouan, 2020; Spoorenberg and Skirbekk, 2025). While women in most European countries typically had their first child in their early to mid-twenties in the 1970s, the average age at first birth is now approaching or exceeding 30 (HFD, 2026). In the early 2020s, first births after the age of 35 accounted for 10–20% of the total fertility rate (TFR) in most high-income countries, and for 30% of the TFR in Italy, Spain and the Republic of Korea (HFD, 2026).

This long-term trend has had a profound impact on people’s reproductive lives. On an individual level, delaying fertility can increase the risk of infertility, miscarriage and health issues for both mother and child (Myrskylä et al., 2017). Consequently, more people may be unable to have as many children as they had hoped. At an aggregate level, delays in fertility timing result in short-term declines in the TFR, and also appear to reduce the TFR of cohorts over the long term (Beaujouan, 2023; Sobotka, 2017).

Delayed reproduction has multiple causes, reflecting both changes in people’s lives and broader transformations in the social contexts in which fertility decisions are made. The expansion of educational and employment opportunities for women is widely recognised as a key driver of delayed first birth (Kreyenfeld et al., 2012; Ní Bhrolcháin and Beaujouan, 2012). Greater gender equality in education and labour markets, as well as women’s increased empowerment and reproductive autonomy, have enabled later fertility (Goldscheider et al., 2015). Broader transformations in partnership trajectories, labour markets and the transition to adulthood have reinforced this trend (Mills et al., 2011). At the same time, changing aspirations regarding partnership, family and parenthood have contributed to later family formation: the framework of the second demographic transition emphasises the role of shifting values in explaining changes in family behaviour, including the postponement of childbearing (Lesthaeghe, 2010). Yet delayed reproduction is not simply the result of greater choice. It can also reflect structural constraints, including the opportunity costs of combining childrearing with education and career building in young adulthood, financial insecurity and difficulties in establishing stable partnerships or living conditions conducive to parenthood (Pailhé and Solaz, 2012).

Technological change has further reshaped the possibilities and consequences of postponement. The availability of effective contraception has given individuals greater control over the timing of childbearing, while assisted reproductive technology (ART) has enabled some people to pursue parenthood at older ages. In recent years, ART has developed rapidly and become more widely available: across Europe, 1–7% of births in 2019 could be attributed to ART (The European IVF Monitoring Consortium (EIM) for the European Society of Human Reproduction and Embryology (ESHRE) et al., 2023). An increasing proportion of these births are to women over the age of 35 (Ben Messaoud et al., 2020). These technologies have prompted important questions, including about their affordability and demographic impact. The current and future use of ART raises many ethical and moral issues that may prove difficult to resolve (Frith et al., 2022; Mertes and Pennings, 2011; van de Wiel, 2020).

Although past research has identified important causes of delayed reproduction, the complexities of this phenomenon have not been fully captured. We have identified five key challenges and unresolved issues relating to delayed reproduction that will shape the research agenda over the next few decades. We outline these issues here to initiate discussion before providing a more detailed overview of the topics covered by the papers in the Special Issue.

This Special Issue engages with these challenges by examining whether and when people have children; how their reproductive intentions evolve; and how postponement affects their chances of conceiving and having a live birth. It also brings together new empirical and conceptual perspectives to reframe delayed reproduction not simply as a demographic trend, but also as a process that is embedded in the life course and is central to contemporary fertility patterns and reproductive experiences.

We have organised the contributions to this Special Issue around three broad themes relating to delayed reproduction. The first theme revisits some of the drivers of delayed fertility, offering both quantitative and qualitative perspectives. The second theme highlights the complexity of reproductive pathways by examining not only live births, but also the entwined reproductive experiences. The third theme focuses on the implications of delayed fertility and asks whether it should be a cause for concern. Finally, we highlight several issues that remain open and revisit some policy approaches that may help to address the challenges associated with delayed reproduction.

A variety of frameworks are being used to study delayed fertility and how it develops. Asking people about their fertility goals provides valuable insights into whether and when they expect to become parents. Recent evidence suggests that there is increasing uncertainty surrounding fertility choices, and that lifetime childbearing intentions have declined among young adult women and men (Bouchet-Valat and Toulemon, 2025; Dommermuth et al., 2025). These findings are consistent with theoretical perspectives that emphasise the growing role of uncertainty in contemporary life course decisions (Badolato et al., 2025; Vignoli et al., 2020). Nevertheless, rather than signalling a permanent rejection of parenthood, lower intentions at younger ages may instead reflect the postponement of fertility plans in response to uncertainty about future life circumstances. Indeed, pathways to parenthood have become increasingly complex, and fertility goals – including timing intentions – are subject to uncertainty and change over the life course (Bachrach and Morgan, 2013; Hayford, 2009; Ní Bhrolcháin and Beaujouan, 2019; Slabá et al., 2024; Trinitapoli and Yeatman, 2018). Using panel data from Germany, Shalini Singh’s contribution (this volume) shows that although individuals typically plan to become parents earlier in life, they frequently revise these plans as their circumstances change – i.e. they postpone their intended age at parenthood, especially in response to their partnership status. Therefore, delayed reproduction can be understood as a consequence of changing reproductive preferences and uncertain intentions in young adulthood, as well as repeated revisions to fertility intentions throughout life.

Alongside the traditional narrative of women’s evolving circumstances, alternative frameworks have expanded their scope to encompass women’s partners, the trajectory of women’s relationships and couples’ social status (Miller and Pasta, 1995; Trimarchi and Van Bavel, 2020). Concepts focusing on gender equality and gender relations have emphasised the impact on fertility behaviour of the unequal domestic division of labour, differences in partners’ ages and educational attainment and differences in women’s and men’s socioeconomic conditions (McDonald, 2013). In this volume, M-C Compans, Alessandra Trimarchi and Éva Beaujouan show that age differences between partners matter for the transition to the first birth when unions are formed after age 30. In more gender-equal Nordic countries, both age homogamy (the partners are similar in age) and age hypogamy (the woman is older than the man) are associated with a higher likelihood of having a first birth for women who partnered later in life. In contrast, in other European regions, couples who adhere to more conventional age patterns, in which the man is moderately older than the woman, are more likely to have a first birth.

Other frameworks pay attention to the importance of kin and social networks in family formation and fertility behaviour (Balbo and Barban, 2014; Lois and Arránz Becker, 2014; Pessin et al., 2022; Sear, 2017). In her Debate contribution (this volume) Anna Rotkirch emphasises the importance of social connections for fertility behaviours and timing. She discusses how perceived social norms and levels of institutional and familial support may influence a person’s reproductive desires, and how the fertility behaviour of peers may trigger the decision to become a parent at a given time.

The impact of education, employment, gender and other socioeconomic and demographic characteristics on individual fertility decisions varies across populations. For example, the relationship between women’s employment and the timing of childbirth is influenced differently by gender dynamics within couples in different welfare state contexts (Badolato et al., 2024). Furthermore, whether later births are the result of increased choice or less deliberate decision-making may depend on a person’s socioeconomic status and level of education (Miettinen and Jalovaara, 2020). In this volume, Nadia Sturm, Alessandra Trimarchi and Jan Van Bavel show that educational differences in women’s first birth transitions can be partly explained by shifts to a positive educational gradient in union formation in western and southern Europe, and that women with higher education continue to have children later than their less educated counterparts. Migration background also influences fertility timing, with the timing varying depending on a woman’s country of origin, migration trajectory (including her age at migration and reason for migrating) and socioeconomic status (Bueno et al., 2023). Leen Marynissen, Karel Neels and Jonas Wood in this volume reveal distinct age profiles of childbearing by education level, country of origin and migrant generation in Belgium. Such a detailed analysis, based on register data, highlights that the category of “migrants” encompasses heterogeneous groups with various fertility age patterns.

Two mixed-methods studies on Latin America provide further insight into individuals’ fertility timing decisions and their context-specific nature. Robin Cavagnoud’s multigenerational study of Peruvian women (this volume) challenges the notion that educational attainment directly influences fertility timing by providing evidence of variation across generations. This relationship is shaped by evolving structural constraints, cultural models and degrees of reproductive agency. Nathaly Llanes-Díaz, Víctor M. García-Guerrero and Paula Martes-Camargo (this volume) explore the mechanisms influencing the intentions to postpone or limit fertility among women of reproductive age in Mexico City. They demonstrate the joint influence of partnerships, uncertainty, individualism and the burden of parental responsibilities.

Conceptually, having a child can be understood as a process that can be broken down into multiple potential steps: the emergence of a desire for a child; the formation of an intention to have one; active attempts to conceive; and, ultimately, a live birth. Individuals may not experience all of these steps, and some may not achieve a live birth. Data capturing all these stages are rare, and research often analyses only a subset of the sequence. Additionally, as information on this process is often collected for women only, men’s perspectives may be missing.

One notable gap in the data concerns when people start trying to conceive. There is little high-quality data available on this topic (Beaujouan et al., 2025). Gert Stulp, Rolf Granholm, Amke M. G. van Tintelen and Zoltán Lippényi (this volume) have developed a microsimulation approach based on Dutch data to address this issue. They estimate that the average age at which women first attempt to conceive has increased from 26.7 years for those born in 1960 to 28.6 years for those born in 1980. Despite this postponement, the average duration between attempting to conceive and actually conceiving has remained stable. The authors suggest that this constant duration may be observed because at older reproductive ages, only the more fertile succeed in conceiving and having children, while the less fertile often remain childless. Amanda Jean Stevenson, Leslie J. Root and Jane Menken (this volume) examine age patterns of fecundability (probability of achieving a conception) using a simulation, and the results indirectly support this assumption. They find that much of the observed decline in mean fecundability at older ages is due to a higher percentage of women with lower underlying reproductive capacity attempting to conceive at these ages. The most fertile women have already had a spontaneous conception or immediately succeeded in conceiving at earlier ages.

During the process of trying to have children, women may face reproductive disruptions such as infertility, pregnancy loss or abortion. Nadja Milewski and Jasmin Passet-Wittig (this volume) propose an analytical framework to re-integrate such experiences into the analysis of birth behaviour and outcomes. Applying this framework to German panel data, they show that women of higher reproductive ages are at high risk of having adverse experiences and no births. Éva Beaujouan and Shalini Singh (this volume) provide additional information on these challenges, demonstrating that the proportion of individuals attempting to conceive for more than two years increases significantly with age. In cross-sectional studies of infertility, this leads to selection effects and length bias, whereby older respondents are more likely to be observed as infertile due to spending a longer time in that state. Findings vary across countries, highlighting the cultural variation in the interpretation of constraints to reproduction and in responses to survey questions on these topics.

Jitka Slabá, Anna Šťastná and Jiřina Kocourková’s study in this volume contributes to our understanding of the implications of various reproductive experiences (e.g. induced abortion, stillbirth, miscarriage and infertility) on the timing of a second birth. Unexpected reproductive events generally slow the transition to the next birth, but women who have experienced a miscarriage or abortion for medical reasons before their first birth tend to transition to a second birth faster, possibly due to a catch-up effect. The mode of delivery of the first birth (vaginal versus interventional) also appears to be associated with intentions to have a second child, as demonstrated by Alessandra Minello, Francesca Tosi, Elena Vettoretto, Chiara Ludovica Comolli, Gianpiero Dalla-Zuanna and Livia Elisa Ortensi (this volume) in the Italian context.

Finally, studying the reproductive sequence provides insight into whether and when people want to have children, and whether they eventually have the number of children they desire. Unrealised fertility is generally sizeable, depending on the context, and tends to be higher among individuals who have experienced infertility (Lazzari and Beaujouan, 2026; Yeatman and Smith-Greenaway, 2025). Additionally, the age considered as optimal for childbirth is typically lower than the average age at which women actually give birth (Lazzari et al., 2025). Whether such gaps reflect constrained choices, preference revision or measurement artefacts is unclear. Kathleen Broussard (this volume) reviews the methodological choices involved. Drawing on US data, she demonstrates how the use of different measurements can significantly impact estimates of unrealised fertility and their associations with various social and reproductive health characteristics.

Taken together, these articles highlight the reproductive challenges people face when childbearing is delayed. As these experiences are embedded in individuals’ life courses, interpretations of survey questions can be subjective, and reports of consequences can differ. However, some patterns do emerge, notably that reproductive delays lead to more frequent adverse reproductive outcomes and can sometimes hinder people’s ability to have a child.

Delayed reproduction is closely associated with lower completed fertility, as the reproductive window narrows and the risk of infertility increases with age. The transition to higher-order births may be particularly affected, as an increasing number of people who become parents late in life are attempting to have a second or third child when they are already approaching the limits of their reproductive lifespan (Winkler-Dworak et al., 2024). Furthermore, some individuals may choose not to have children if they have not achieved their ideal circumstances for doing so by a certain age (Berrington, 2004; Morgan, 2003).

Research has consistently shown a discrepancy between people’s desired and actual number of children (Yeatman and Smith-Greenaway, 2025). Fertility postponement probably contributes to this gap by increasing the likelihood of encountering obstacles to having children before reaching the desired family size. Peter Fallesen, Lars Dommermuth, Julia Hellstrand, Emil Simonsen, Lisbeth Trille Gylling Loft and Laust Hvas Mortensen (this volume) examine the projected gap between measures of ideal family size and completed fertility in Denmark and Norway. They demonstrate that the gap is expected to increase in both of these Nordic contexts, and that it is driven by a smaller average family size due to a significant decrease in fertility before the age of 30.

Because age-related infertility increases with delayed childbearing, there is a growing demand for ART. Despite the key role these technologies play for some individuals who otherwise would not have become parents, their aggregate demographic impact on fertility levels is limited (Chanfreau et al., 2025). Jiřina Kocourková’s Debate article in this volume highlights that medical technologies cannot provide an adequate response to the social causes of delayed reproduction. The technologies developed in response to age-related infertility, such as oocyte cryopreservation (also known as social egg freezing) and egg donation, raise further questions that were explored during the round table organised at the 2025 Wittgenstein Centre conference in Vienna, and that are summarised by Nina Dippold and Éva Beaujouan in this volume. Will such developments extend the age limits of childbearing, and what will the consequences be? Could the commercialisation of these technologies deepen social inequalities in access? These questions, in turn, raise fundamental questions of reproductive justice, as Katherine I. Tierney and Arthur L. Greil discuss in their Debate article (this volume). Without equitable access, ART use could become a privilege of the more affluent rather than representing a genuine expansion of reproductive possibilities for all. In her Debate article, Lone Schmidt (this volume) discusses whether social inequalities in access to ART could be alleviated through the expansion of coverage of assisted reproduction to include “new” family types (single individuals, same-sex couples) and the removal of barriers to access for disadvantaged groups.

The spread of ART, its accessibility and its consequences should remain topics of discussion. Indeed, the increasing use of ART has prompted speculation, albeit with little empirical evidence, that it may contribute to the postponement of childbearing. Individuals generally lack awareness of fertility issues, particularly regarding the age-related decline in fecundability (Bunting et al., 2013; Hammarberg et al., 2017). Providing them with the option of technological assistance may create the illusion that they will still be able to have a child much later, thereby encouraging them to defer childbearing (Compans et al., 2026; Rainer et al., 2011; Ziebe and Devroey, 2008).

In addition to infertility and ART, pregnancies at advanced maternal ages have been extensively studied due to the increased clinical risks associated with later childbearing, such as the risk of adverse perinatal outcomes for both mother and child (Goisis, Remes, et al., 2017). Using Spanish birth statistics data, Marta Seiz (this volume) shows that higher maternal education protects against adverse perinatal outcomes across ages. However, this is not sufficient to counteract the negative effects of delayed childbearing in Spain.

Discussions about the consequences of delayed reproduction often focus on the risks and challenges involved. The tendency to postpone childbirth has broader implications for population dynamics, extending beyond the impact on fertility rates and fuelling concerns about population ageing (Skirbekk, 2022). Fewer and later births could reshape population age structures, which would have implications for dependency ratios and the sustainability of welfare systems. In this volume, Xueqing Wang and Leng Seong Che consider the consequences for intergenerational relationships in China, highlighting that differences in fertility postponement patterns across rural and urban regions will affect the availability of future caregivers for an ageing population.

The perceived and actual disadvantages of delayed fertility often dominate the scientific literature and public discussion. However, delayed fertility also has various advantages. On an individual level, having children later in life has been associated with higher levels of parental education, greater financial stability, more established career paths and more stable relationships at the time of birth (Myrskylä et al., 2017; Sigle and Kravdal, 2021). These factors have been shown to have a positive impact on child development outcomes (Goisis, Schneider, et al., 2017). At the macro level, Hal Caswell (this volume) formally examines population dynamics, showing that delayed reproduction can temporarily reverse population decline in some countries with below-replacement fertility, such as Japan and Slovakia. In addition, the factors associated with delayed reproduction, such as increased female education and labour force participation, can be viewed as indicators of social progress. Guido Pennings in this volume takes up this interpretation of delayed reproduction as a positive symptom of enhanced opportunities for women in the public sphere. In his Debate article, he also highlights the potential environmental and reproductive autonomy benefits of trends in delayed reproduction. Consistent with these observations, it has been argued that lower fertility and its consequences for population shrinkage, when accompanied by rising human capital, should be welcomed (Skirbekk, 2022). From this perspective, delayed reproduction is less a problem to be solved than a development to be understood.

This Special Issue brings together diverse contributions that examine delayed reproduction as a defining feature of contemporary demographic change. The Research articles provide rich empirical evidence across the life course, examining fertility intentions and their evolution, partnership dynamics, age-specific fecundability and parity progression, as well as difficult reproductive experiences such as infertility or miscarriage. Particular emphasis is placed on heterogeneity and social inequality within and across populations. Drawing on data from Europe, the Americas and Asia, the Special Issue highlights that delayed reproduction is a widespread trend with significant consequences for individuals and societies, albeit with specificities across national contexts. The Debate articles further illuminate the tensions between people’s aspirations, structural constraints and opportunities, reproductive justice and the limitations of ART. Together, these contributions lay the groundwork for a critical reflection on whether delayed reproduction should be understood as a deliberate choice or as a socially patterned response to broader economic and institutional contexts.