Across high-income countries, women and couples are having children later than ever before, sometimes turning to assisted reproductive technologies (ART). At older ages, however, Ester Lazzari and Luzia Bruckamp say, these treatments are effective only with donor eggs.
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).