In 1992, only about 11,000 women in the UK started their first infertility treatment cycle. By 2018, that number had more than doubled, and births conceived through ART accounted for 3.0% of the national fertility rate, up from just 0.3% in 1991. ART’s contribution is especially pronounced at older ages. In 2018, around 15% of fertility at ages 45–50 was attributable to ART, relative to 5.5% at ages 35–37, 7.2% at 38–39, 7.8% at 40–42, and 8.4% at 43–44. 

Most ART-conceived births result from treatments using women’s own eggs. However, the contribution of donor eggs to the total fertility rate has steadily increased over time. The contrast by age is striking: donor-egg treatments are used much more frequently from age 43 onward, and they account for the vast majority of ART births at these ages (Figure 1).

ART success rates decline steeply with age unless donor eggs are used

ART success rates using a woman’s own eggs decline sharply after age 35 and fall to below 5% for women aged 43 and over. By contrast, treatments using donor eggs from younger women maintain consistently high success rates at all ages (Figure 2). This stark difference creates two distinct reproductive pathways when using ART. On one side, autologous ART (using one’s own eggs) works relatively well up to the late 30s but then drops off dramatically. On the other side, ART with donor eggs remains effective even into the mid- and late-40s. In a recent study, we show that from age 43 onward, most ART-conceived births come from donor eggs (Bruckamp and Lazzari 2025). By ages 45–50, donor eggs account for more than 90% of all ART births. In other words, for older women, ART success depends almost entirely on access to young eggs – whether through donation or from eggs frozen earlier in life.

Why donor eggs make such a difference

An ART cycle involves several steps: ovarian stimulation, egg retrieval, fertilization, embryo development, and embryo transfer. For women in their 40s using their own eggs, obtaining viable eggs often fails. By contrast, donor egg cycles start with high-quality eggs from younger women, allowing the process to skip the step most vulnerable to age-related decline. In fact, age-related declines in fertility are driven almost entirely by reductions in egg quality and quantity, while the ability to carry a pregnancy is much less affected. This is why, in our sample, women aged 45–50 using donor eggs had pregnancy rates above 30%, while those using their own eggs had rates of only 2–3%. Technological advances cannot compensate for declines in egg quality. Instead, ART success at older ages strongly relies on the use of younger eggs.

A growing demographic impact but limited by biology

ART is making a small but steadily growing contribution to fertility rates in the UK, mirroring patterns observed in other high-income countries. While ART has helped support fertility among those who postpone childbearing, our study shows that its impact remains modest and highly dependent on the type of treatment used. 

The increasing reliance on donor eggs raises new demographic, ethical, and policy considerations. Egg donor supply is limited: the UK tightly regulates egg donation, compensation to donors is capped, and only about 6% of ART cycles involved donor eggs in 2019. Yet, demand is likely to continue to grow as childbearing continues to be delayed. Donor-egg pregnancies also involve additional medical and ethical complexities, including higher risks of pregnancy complications and issues related to donor rights, offspring identity, and the regulations governing third-party involvement in reproduction. 

Egg freezing may offer an alternative, as it allows women to preserve fertility at younger ages for use later in life. Evidence suggests that success rates with frozen eggs reflect the biological age at which the eggs were retrieved, meaning that freezing in the early 30s could, in principle, reduce the need for donor eggs later on. However, egg freezing is costly, rarely publicly funded, and its long-term success rates remain uncertain, especially when eggs are frozen at younger ages and used a decade or more later.

Better public health communication is essential

While previous research has shown that ART can contribute to fertility recuperation at older ages (Lazzari et al. 2023), our study clarifies that at very advanced ages this recuperation is driven almost entirely by the use of donor eggs. This distinction is not widely understood, yet it is crucial both for anticipating the future demographic role of ART and for helping individuals make informed reproductive decisions. 

Research consistently shows that most people are unaware that ART success at older ages depends almost entirely on the use of donor eggs, and knowing this may meaningfully change their expectations and plans. Improving communication about age-related fertility decline, realistic ART success rates, and the central role of donor eggs at older ages is therefore essential for informed reproductive decision-making. At the same time, policies that enable those who wish to have children earlier (such as secure employment, affordable housing, and accessible childcare) remain critical, since ART can support family building but cannot fully compensate for the biological constraints imposed by postponed childbearing.

References

Bruckamp L., Lazzari E. (2025) Shifting the reproductive window: The contribution of ART and egg donation to fertility rates in the UK. Popul Stud; 1–13. doi:10.1080/00324728.2025.2561595

Lazzari E., Potančoková M., Sobotka T. et al. (2023) Projecting the Contribution of Assisted Reproductive Technology to Completed Cohort Fertility. Popul Res Policy Rev 42, 6. https://doi.org/10.1007/s11113-023-09765-3

Office for National Statistics (2025). Births in England and Wales: Birth Registrations. (Accessed: 25 November 2025).

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When parents or parents-in-law experience a decline in health, adult children often step in to provide care. This new role can profoundly affect their plans for the future, including the decision to start or expand their own families. In a recently published study (Lazzari and Zurla 2024), we explored how Australian men and women expecting to have children changed their plans after becoming care givers to their parents. 

The issue is especially important today as many people are delaying parenthood and, by the time they are ready to start a family, their parents will be older and more likely to need care. 

Balancing caregiving and family plans

When a parent’s health deteriorates, adult children may take on caregiving duties that are both emotionally and physically demanding (Fortinsky et al. 2007). If becoming a caregiver happens at a time when they are planning to have children, it could negatively affect those plans. Two main reasons explain this link. First, caring for an elderly parent takes time and energy, leaving less room to focus on other goals, like building a family. Second, many people rely on their parents for childcare once they have children. If their parents are unwell, this support may no longer be available, leading them to revise their fertility plans.

Previous research in Europe has shown that the informal childcare provided by grandparents often encourages their adult children to have kids (e.g., Aassve et al. 2012; Rutigliano 2024; Rutigliano & Lozano, 2022; Tanskanen & Rotkirch 2014). This is likely true also in Australia, the setting of this study, where grandparents are the most common childcare providers (Baxter 2022). 

Parental caregiving may also have positive effects by prompting psychological changes that positively influence fertility plans. For instance, adult children who became caregivers may feel more motivated to continue the family line or to give their parents the joy of becoming grandparents (Rackin & Gibson-Davis 2022).

Fertility expectations decline after caregiving begins 

In our study, we examined these connections using survey data from Australia collected between 2001 and 2021. We focused on a sample of men and women of reproductive age who had positive childbearing expectations and analyzed how these expectations evolved over time. We used a difference-in-differences model which compared changes in fertility expectations between two groups: a treatment group consisting of individuals who became caregivers and a control group consisting of similar individuals who did not become caregivers. If becoming a parental caregiver affects fertility expectations, we would expect to see a divergence in the trajectories of the two groups after individuals in the treatment group take on caregiving responsibilities. Moreover, if these two groups have similar trajectories before the event, this suggests that they would have followed comparable patterns if not for their differing experiences with caregiving. 

Results are represented in Figure 1. The x-axis indicates the time (in years) relative to the onset of becoming a parental caregiver. The dashed gray line indicates where we would expect the regression coefficients to fall if caregiving had no effect on fertility expectations. The figure indicates that becoming a caregiver results in an immediate and substantial decline in expectations, and that this negative effect intensifies over time. On average, fertility expectations decrease by approximately 7% within the first two years and by 20% three years after the caregiving responsibility begins. 

In a separate analysis, we explored how these results vary based on whether caregivers are childless or already have one child. No relevant difference emerges between the two groups in the first two years following the caregiving event. However, after three years, parents with one child experience a more pronounced decline in fertility expectations. This pattern could be attributed to stricter birth timelines among parents. Typically, the interval between the first and second child is 2 to 4 years, and missing this window may lead to a larger drop in expectations compared to individuals with no children.

Implications 

While previous research has identified many factors that can lead people to revise their fertility plans, the role played by parental caregiving responsibilities has not been specifically investigated. In this study, we shed light on this link by presenting evidence that an increase in caregiving responsibilities toward parents is likely to have a negative impact on fertility expectations. 

Although grandparents can serve as an important source of support for their children planning to start a family, their declining health may present obstacles to family formation. Since health tends to deteriorate with age, individuals who delay family formation are more likely to face the caregiving needs of their aging parents when planning their own families. This may make parental caregiving an increasingly important factor in understanding childbearing choices and suggests that public interventions supporting adult children in their caregiving roles could help alleviate some of the pressures when making childbearing decisions.

References

Aassve A., Arpino, B., & Goisis, A. (2012a). Grandparenting and mother’s labour force participation: A comparative analysis using the Generations and Gender Survey. Demographic Research, 27(3): 53-84.

Fortinsky, R. H., Tennen, H., Frank, N., & Affleck, G. (2007). Health and Psychological Consequences of Caregiving. In C. M. Aldwin, C. L. Park, & A. Spiro III (Eds.), Handbook of health psychology and aging (pp. 227–249). The Guilford Press.

Lazzari, E. & Zurla, V. (2024). The Effect of Parental Caregiving on the Fertility Expectations of Adult Children. European Journal of Population, 40 (online first).

Rackin, H., & Gibson-Davis, C.M. (2022). Familial deaths and first birth. Population and Development Review, 48(4): 1027-1059.

Rutigliano, R. (2024). Do grandparents really matter? The effect of regular grandparental childcare on the second-birth transition. European Sociological Review, 40(5), 772-785.

Rutigliano, R., & Lozano, M. (2022). Do I want more if you help me? The impact of grandparental involvement on men’s and women’s fertility intentions. Genus, 78: 13.

Tanskanen, A.O., & Rotkirch, A. (2014). The impact of grandparental investment on mothers’ fertility intentions in four European countries. Demographic Research, 31: 1-26.

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Over the past generation, fertility treatment has been revolutionized by the advent and development of assisted reproductive technologies (ART), such as in vitro fertilization (IVF). These technologies have accounted for 4-5% of the Australian total fertility rate each year over the last decade (Lazzari et al. 2021). Unlike other forms of fertility treatments like ovulation induction (OI) and intrauterine insemination (IUI), ART involves fertilization outside the body (in vitro), followed by the transfer of resulting embryos into the uterus, with the aim of achieving a pregnancy.  Together, ART, OI, and IUI are often referred to as medically assisted reproduction (MAR).

Although national ART registries provide some insights into the contribution of ART to the number of births in a country, little is known about their role, along with other forms of MAR, on childbearing timing and family size. This represents a significant gap in demographic and population policy knowledge, particularly given the growing evidence of rising infertility due to childbearing postponement (Habbema et al. 2015). At the same time, the use of fertility treatments is increasing globally (Chamber et al. 2021b), and several countries are showing a growing interest in subsidizing ART treatment as a pronatalist policy to counteract fertility decline (Gray et al. 2022).

In a recent study (Choi et al. 2023), we investigated how the mode of conception of the firstborn child, whether through MAR or natural conception, and mother’s socioeconomic status impact on family formation, including childbirth timing (postponement and recovery) and completed family size.

We used a unique longitudinal Australian dataset covering all major forms of MAR to examine their contribution to these fertility dynamics (Chambers et al. 2021a). Australia provides an ideal setting to explore the potential impact of MAR on family formation, as funding for MAR treatment is supportive, and utilization rates are relatively high (Chambers et al. 2021b). 

Completed family size and mean age at first birth by mode of conception

Mothers who used MAR treatment to conceive their firstborn child were older and had a smaller completed family size by the end of their reproductive lives than mothers giving birth to their first child naturally. This effect was more pronounced among mothers who used ART compared with those who used more traditional fertility treatments, such as OI and IUI. In particular, the mean maternal age at first birth was higher for ART mothers: 34.6 years vs 31.0 years for OI/IUI mothers and 28.7 years for mothers of a naturally conceived child. Moreover, ART mothers achieved a smaller completed family size: 2.20 children against 2.98 and 3.23, respectively, for OI/IUI mothers and mothers of a naturally conceived child.

Fertility postponement and recuperation by mode of conception

Figure 1 illustrates the patterns of fertility postponement and recovery for mothers who had fertility treatment and those who conceived naturally. The comparison with the reference group of natural-conception mothers enables the visualization of the gap in completed family size between different groups of mothers by mode of conception of their firstborn child over their reproductive ages. 

Mothers who had fertility treatment (ART and OI/IUI) had 0.68 and 0.24 fewer children, respectively, than natural-conception mothers. Additionally, ART mothers postponed childbearing for longer than  those who underwent OI/IUI. ART mothers had their first child at age 36.4 years, versus 30.3 years for OI/IUI mothers.

The impact of maternal socioeconomic status

Mothers residing in more socioeconomically advantaged areas who used ART to conceive their firstborn child were about 3 years older than ART mothers residing in less advantaged areas. Despite this age difference, the fertility gap with respect to mothers conceiving their first child naturally was smaller for ART mothers in more advantaged areas than for ART mothers in less advantaged areas (0.43 fewer children versus almost one less child, respectively) (Figure 2). For OI/IUI mothers on the other hand, by the end of the reproductive years, the impact of maternal socioeconomic status on the fertility gap with respect to mothers conceiving their first child naturally was relatively small (Figure 2).

Missed births and reproductive inequalities

The enduring discrepancy in the final number of children among mothers who used ART or other types of fertility treatments for their first birth and those who conceived naturally highlights the importance of understanding the natural decline in fertility with age, as well as the limitations of relying on MAR in achieving a desired family size. There is a pressing need to enhance awareness and education on these issues. 

It is also worth noting that not only the mode of conception, but also the mother’s level of socioeconomic advantage influences family formation dynamics. The smaller completed family size of mothers of lower socioeconomic status compared with mothers of higher socioeconomic status – despite both conceiving their firstborn child through ART and the latter starting their families on average three years later – suggests the existence of continued socioeconomic inequalities in the ability to achieve the desired family size through ART, even in countries with supportive funding environments like Australia. 

References

Chambers, Georgina M, Choi, Stephanie KY, Irvine, Katie, Venetis, Christos, Harris, Katie, Havard, Alys, Norman, Robert J, Lui, Kei, Ledger, William, and Jorm, Louisa R. (2021a). A bespoke data linkage of an IVF clinical quality registry to population health datasets; methods and performance. International Journal of Population Data Science, 6(1): 1679. 

Chambers, Georgina M, Dyer, Silke, Zegers-Hochschild, Fernando, de Mouzon, Jacques, Ishihara, Osamu, Banker, Manish, Mansour, Ragaa, Kupka, Markus S, and Adamson, David G. (2021b). International committee for monitoring assisted reproductive technologies world report: assisted reproductive technology, 2014. Human Reproduction, 36(11): 2921-2934. 

Choi, Stephanie KY, Lazzari, Ester, Venetis, Christos, and Chambers, Georgina M. (2023). Childbirth timing and completed family size by mode of conception – the role of medically assisted reproduction: a population-based cohort study in Australia. The Lancet Regional Health Western Pacific

Gray, Edith, Reimondos, Anna, Lazzari, Ester, Breunig, Robert, Steinhauser, Ralf, Zhang, Jacquelyn, Biddle, Nicholas, and Gray, Matthew. (2022). Impact of policies on fertility rate.

Habbema, J Dik F, Eijkemans, Marinus J C, Leridon, Henri, and te Velde, Egbert R. (2015). Realizing a desired family size: when should couples start? Human Reproduction, 30(9): 2215–2221. 

Lazzari, Ester, Gray, Edith, and Chambers, Georgina M. (2021). The contribution of assisted reproductive technology to fertility rates and parity transition. Demographic Research, 45(35): 1081–1096.

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In high-income countries, completed fertility has declined substantially among the post baby boom cohorts (Zeman et al. 2014). While such decline may be due to several factors, the expansion in women’s education is often recognised as one of its most important drivers. In virtually all developed countries, an extensive literature has consistently found support for an inverse relationship between education and fertility. Reasons for this include the increased opportunity cost of having children, different preferences regarding ideal family size, changes in childbearing timing and gender values. 

With the only exception of Finland, the educational gradient in relation to completed family size is clearly visible in the data displayed in Figure 1: completed fertility tends to be higher among lower educated women. At the same time, an overall downward trend can be identified across all groups, irrespective of the level of education. 

This raises a key question with respect to the education-fertility relationship: to what extent does the decrease in fertility reflect changes in the educational composition vs. changes in fertility behaviour within educational categories? In a recent study, we disentangle the relative contribution of these two components in eleven low-fertility countries (Lazzari et al. 2021).

Permanent differences or convergence?

The size of the educational gradient varies across settings and important differences exist due to contextual factors, such as a country’s welfare regime.  In Australia, Ireland, and Spain, educational groups have experienced analogous fertility declines, and maintained similar relative fertility levels over time. By contrast, in South Korea completed family size across educational strata has been gradually converging towards very low fertility levels. In Finland, there is no evidence of a negative association between education and fertility, while in Hungary women have experienced a widening of the educational differentials. Overall, these patterns reflect the complexity of the link between education and fertility.

When the completed fertility rate is decomposed into compositional and behavioural components it appears that, overall, educational expansion is a relatively modest force behind fertility decline, particularly in countries and periods characterised by small and diminishing differentials across educational groups (Figure 2). By contrast, the persistence of educational differentials in cohort fertility coupled with women’s educational expansion are associated with a larger compositional contribution. The decomposition method is explained in Lazzari et al. (2021).

Number of children

Different combinations of changes in first, second, third and higher order births can lower fertility levels. As displayed in Figure 3, declines in third and higher-order births were the most important component of fertility change in most cohorts and educational groups, while changes in the transition to first and second births varied substantially across countries and by education. 

Interestingly, in Hungary, Ireland, South Korea and Spain, distinct fertility developments by education are observed among older cohorts. Among the most recent cohorts, however, more similar patterns have emerged. In all educational groups, the share of women remaining childless has increased, and the share of those transitioning to a second child has declined. This may reflect the existence of increasing market pressures and constraints to childbearing of women with low education in these settings.

Future prospects

As tertiary-educated women already represent a large share of the overall population, it is clear that the importance of the compositional component as a driver of fertility decline will decrease. Highly educated women today represent a vast and heterogeneous group, while low educated women are a very selected category (Adsera 2017). The future study of the link between education and fertility should include alternative measures to define educational groups and develop alternative theories to explain fertility patterns by education, as the educational gradient has substantially declined or even disappeared in some countries.  

References

Adsera, A. (2017). The future of fertility of highly educated women: The role of educational composition shifts and labour market barriers, Vienna Yearbook of Population Research 15: 19–25.

Lazzari, E., Mogi, R., and Canudas-Romo, V. (2021). Educational composition and parity contribution to completed cohort fertility change in low-fertility settings. Population Studies, 75(2): 153-167.

Zeman, Krystof, Zuzanna Brzozowska, Tomás Sobotka, Éva Beaujouan, and Anna Matysiak. 2014. Cohort Fertility and Education Database. Methods Protocol.

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In Australia, as in most other high- and middle-income countries, assisted reproductive technologies (ART), such as in-vitro fertilisation (IVF), continue to play an increasing role in helping individuals to have much wanted children. Latest estimates indicate that over the last two decades, the number of ART cycles performed in Australia has increased by almost 200%, with a steadily growing chance of treatment success, particularly for women of advanced reproductive age (Newman et al. 2021).

An important driver of the uptake of ART treatment is the major demographic and social trend towards delayed childbearing (Beaujouan 2020). For instance, in Australia, over the past three decades, the fertility rate of women aged 35 to 39 has more than doubled, and for women aged 40 to 44 it has tripled (ABS 2018). The ability to conceive a child naturally declines with female age, particularly after age 35 (Eijkemans et al. 2014). Thus, an increasing number of women experience age-related infertility and turn to assisted reproduction in the hope of having a baby. 

Women having a child with ART are mostly first-time mothers

In a new study, we describe the characteristics of women who conceived using ART in Australia and quantify the impact of these births on the total fertility rate in recent years (Lazzari et al. 2021). We find that the proportion of first-borns is markedly higher among those giving birth using ART than among all women giving birth in the population (Figure 1). For example, among women of advanced maternal age (40 and above), two-thirds of those who have an ART-conceived birth are first-time mothers compared to just one in four of all women giving birth. This trend suggests that ART treatment is mostly contributing to a reduction in childlessness by helping women to have their first or only child, rather than increasing family size.

The demographic contribution of ART increases with mother’s age 

We also find that that one in 20 births in Australia are a result of ART, corresponding to almost 5% of the total fertility rate. Moreover, the likelihood that a child is conceived using ART treatment increases significantly with mother’s age. For instance, in 2017, only 1 in 100 babies born to women aged below 30 were ART-conceived, compared to one in 5 born to women aged 40 to 44 and one in 3 born to women aged 45 and above. 

As displayed in Figure 2, the recent decline in the total fertility rate, from 1.95 in 2010 to 1.74 in 2017, is explained by a substantial reduction in fertility rates at younger ages, followed by only a partial recovery later in life. Yet, over this period, the increasing number of ART-conceived births to women in their mid-30s and over has greatly supported fertility rates at older ages, marginally offsetting the ongoing decline in naturally conceived births. For women in their late 30s or older, increases in fertility rates are almost entirely driven by the growing use of ART. These trends suggest that assisted reproduction is playing a meaningful role in contribtuing to Australia’s fertility rate by allowing a proportion of women to achieve parenthood at advanced maternal age.  

An opportunity to reduce the gap between fertility intentions and realisation

Both social and biological aspects are important for understanding fertility trends. Against the backdrop of the continuing trend to delayed childbearing, the contribution of assisted reproduction will likely play an even greater role in supporting fertility rates in the future in societies where supportive social policies for the use of ART are in place. Australia is unique in that its national health insurance scheme, Medicare, subsidizes two thirds of the costs for all ART treatments, with no restriction based on age or number of treatments already performed, criteria often used to ration funding in most other countries. Indeed, largely because of its supportive funding environment, Australia has one of the highest ART utilisation rates in the world (Adamson et al. 2018). Thus, our study shows the impact of ART on age-specific fertility rates in a setting of supportive funding for ART and may serve as a case study for other countries considering an increase in ART coverage.

At the same time, it is important that individuals do not delay childbearing in the belief that ART will act as an insurance policy against childlessness. Nor should policy makers rely on ART to fully compensate for fertility decline. Like natural fertility, the success of infertility treatment also declines with age if a woman is using her own eggs. For example, for women aged 30 to 34 years commencing ART treatment, the estimated chance of having a child is 70% compared to only 20% among those aged 40 to 44 (Chambers et al. 2017). Hence, while this study demonstrates the positive impact of ART on fertility rates at advanced maternal age, it should be also noted that ART cannot fully compensate for the births lost due to childbearing delay. Fertility education and policy initiatives should also support individuals so that they can have children when it is biologically desirable for them to do so. 

References

ABS (Australian Bureau of Statistics) (2018). Births, Australia, 2017. Catalogue no. 3301.0. Canberra: ABS.

Adamson, G.D., de Mouzon, J., Chambers, G.M., Zegers-Hochschild, F., Mansour, R., Ishihara, O., Banker, M., and Dyer, S. (2018). International Committee for Monitoring Assisted Reproductive Technology: World report on assisted reproductive technology, 2011. Fertility and Sterility, 110(6): 1067–1080.

Beaujouan, E. (2020). Latest-late fertility? Decline and resurgence of late parenthood across the low fertility countries. Population and Development Review 46(2): 219-247.

Chambers, G.M., Paul, R.C., Harris, K., Fitzgerald, O., Boothroyd, C.V., Rombauts, L., Chapman, M.G., and Jorm, L. (2017). Assisted reproductive technology in Australia and New Zealand: cumulative live birth rates as measures of success. Medical Journal of Australia, 207(3): 114-118.

Eijkemans, M.J.C., van Poppel, F., Habbema, D.F., Smith, K.R., Leridon, H., and te Velde, E.R. (2014). Too old to have children? Lessons from natural fertility populations. Human Reproduction 29(6): 1304-1312.

Lazzari, E., Gray, E. and Chambers, G. M. (2021). The Contribution of Assisted Reproductive Technology to Fertility Rates and Parity Transition: An Analysis of Australian Data. Demographic Research, 45 (9): 1081-1096. 

Newman, J. E., Paul, R.C. and Chambers, G.M. (2021). Assisted reproductive technology in Australia and New Zealand 2019. National Perinatal Epidemiology and Statistics Unit, the University of New South Wales, Sydney. 

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