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A study published in the Lancet Obstetrics, Gynaecology, & Women’s Health looks at levels of infertility in women aged 35-49.
Comments gathered by the Spanish Science Media Centre:
Guillermo Antiñolo Gil, Professor of Obstetrics and Gynaecology at the University of Seville and Head of the Department of Maternal-Foetal Medicine, Genetics and Reproduction at the Virgen del Rocío University Hospital (Seville), says:
“The study is methodologically reliable. It uses the Global Burden of Disease (Global Burden of Disease, GBD 2023) database, covers 204 countries between 1990 and 2023, and applies standard statistical tools that have been properly implemented. Its main contribution is to focus on women aged 35 to 49 — the age group in which the biological decline in fertility really takes its toll — and to project the trend up to 2036. The figures are striking in their magnitude: around 53.6 million women in that age group affected in 2023, with a projection of nearly 79.6 million in 2036, and a shift in the relative burden from less developed countries towards higher-income ones.
These figures should, however, be interpreted with caution, as the indicator does not measure exactly what it appears to. The GBD’s infertility prevalence is a modelled figure that depends to a large extent on whether a woman wishes to have children, seeks medical care and has access to diagnostic services. In other words, it measures not only biological factors but also the seeking of care and the quality of data recording. The best evidence of this is the implausible disparity between similar countries: Belgium is recorded as having 8,499 cases per 100,000 women and Germany 2,195; Spain, with 2,226, lies well below the global average (6,907). I do not believe that a Belgian woman is four times more infertile than a German woman.
It is also worth clarifying what the infertility rate actually means: the study calculates it based on all women aged 35 to 49, not just those trying to conceive, which is what is clinically understood by the term ‘infertility rate’. As the denominator is the entire population of women in that age group, the mere increase in the number of women seeking pregnancy at a later age raises the rate, even if the risk per attempt has not changed; for this reason, the increase should not be interpreted as a rise in the biological risk of infertility.
There are two further points to consider. Firstly, regarding the burden: the study expresses this in disability-adjusted life years (DALYs), but infertility does not result in mortality, meaning that this burden consists entirely of a loss of quality of life; in other words, the GBD treats infertility itself as a disability to which it assigns a weight — a debatable value — and so it should not be compared with that of fatal diseases. Secondly, the study only considers female infertility and excludes the male factor, which accounts for a significant proportion of cases.
In Spain, the decisive factor is not a new biological epidemic, but the postponement of motherhood for socio-economic reasons.
The average age at which women have their first child is around 33; the fertility rate is among the lowest in the world (1.10 children per woman); and one in ten births is now to mothers aged 40 or over; women themselves cite a lack of financial resources, the difficulty of balancing work and family life, and fears about the impact on their careers as the main barriers. That is why the most effective approach is social and preventative, not merely palliative: early information on the decline in fertility with age; measures to tackle the structural causes of delayed childbearing (housing, job insecurity, work-life balance and shared responsibility for care); early reproductive assessment in primary care; honest advice on egg freezing, without presenting it as a guarantee; and more rational and equitable public access to assisted reproduction, without overlooking the male factor. Precision reproductive medicine and genomics also open up new possibilities for better characterising the causes and refining individual prognoses.”
He declares that he has no conflict of interest.
Rocío Núñez Calonge, scientific director of the UR Internacional Group and coordinator of the Ethics Committee of the Spanish Fertility Society, says:
“The study by Yuanyuan Du et al. provides a comprehensive analysis of trends in infertility between 1990 and 2023 among women aged 35 to 49, assessing temporal trends, quantifying regional inequalities, identifying the main associated factors, and determining which countries have the greatest potential for improvement through the analysis of 204 territories within the framework of the Global Burden of Disease(GBD). According to their findings, in 2023 approximately 53.6 million women in this age group were affected by infertility, and projections estimate that this figure could reach 79.6 million by 2036.
The authors highlight that this group of women has received limited attention in epidemiological studies on infertility, despite accounting for a significant proportion of the global burden of disease. However, focusing the analysis exclusively on women aged 35 to 49 introduces certain biases that must be taken into account. Firstly, it is to be expected that this group would have the highest rates of infertility, given that from the age of 35 onwards there is a progressive decline in both ovarian reserve and oocyte quality, with a significant acceleration from the age of 40. Furthermore, the inclusion of women aged between 45 and 49, for whom the probability of spontaneous pregnancy is extremely low, may contribute to an artificial increase in the overall estimate of infertility associated with this age group.
Secondly, although the authors highlight the scarcity of specific studies on fertility in women of advanced maternal age, there are numerous studies that have addressed this issue from a clinical perspective. In this regard, recent studies have demonstrated a progressive decline in reproductive outcomes with age. For example, a study published by Sebastián-León in 2025 (https://www.sciencedirect.com/science/article/pii/S0015028225004388) describes an annual decline of approximately 4.2 per cent in the embryo implantation rate in women over the age of 40, highlighting the impact of reproductive ageing on the outcomes of assisted reproduction treatments.
The study’s main contribution lies in the scope of its international analysis, which enables an assessment of differences across 204 countries and the establishment of future projections regarding the trend in infertility. However, another potential methodological bias must be taken into account: the public health burden of morbidity represented by the proportion of women aged between 35 and 49 affected by infertility (defined according to the GBD as women of childbearing age who are trying to conceive but are unable to become pregnant). This indicator may be influenced by socio-economic and cultural factors, as well as factors relating to access to the healthcare system; furthermore, it disproportionately reflects the situation of older women, who face the greatest difficulty in conceiving.
The study highlights that, although historical differences between low- and high-income regions have narrowed, the burden of infertility is gradually shifting towards higher-income countries. In these contexts, women are more likely to delay motherhood and to access diagnostic tests and fertility treatments. The authors interpret this phenomenon as a consequence of broader social and economic changes, including the postponement of family planning until later in life and greater availability of reproductive services in certain developed settings.
In Spain, as in other developed countries, a significant increase in infertility has been observed among older women. However, it is important to interpret these data with caution: the increase observed in this age group does not necessarily imply an intrinsic rise in infertility, but rather reflects, to a large extent, a progressive delay in the age at first pregnancy driven by social, economic and occupational factors. Consequently, analysing this age group alone may confuse the effect of reproductive ageing with a supposed change in the population’s reproductive capacity.
The authors highlight the urgent need to develop more inclusive reproductive health strategies and to integrate infertility into national and international health agendas. Proposed measures include expanding public coverage of assisted reproductive technologies, investing in technological innovation, promoting informed family planning, strengthening health systems and increasing international cooperation to ensure equitable access to reproductive care.
However, the rise in infertility associated with this age group cannot be addressed solely by expanding the range of assisted reproductive therapy options. Although these techniques are a vital tool for many patients, they do not address the structural cause of the problem. In countries such as Spain, it is also necessary to address the social factors that contribute to delayed motherhood, particularly those relating to work-life balance, economic stability and institutional support for early motherhood.
In short, the study provides relevant information on the global distribution of infertility among women of advanced maternal age and highlights its significant health and social implications, such as population ageing, the growing demand for reproductive treatments and the added pressure on health systems. However, solutions must go beyond the medical sphere and envisage social and structural changes that enable women to exercise their reproductive rights under more favourable conditions”.
She declares that she has no conflicts of interest.
‘Epidemiological trends, disparities, and developmental correlates of infertility in women of advanced maternal age, 1990–2023: a comprehensive analysis within the GBD framework’ by Yuanyuan Du et al. will be published in the Lancet Obstetrics, Gynaecology, & Women’s Health at 23:30 UK time on Monday 6 July 2026, which is when the embargo will lift.