A study warns of a global rise in infertility among women over the age of 35

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 describes an annual decline of approximately 4.2 per cent in the embryo implantation rate in women over 40, highlighting the impact of reproductive ageing on the outcomes of assisted reproductive technologies.

The study’s main contribution lies in the scope of its international analysis, which enables the 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 enhancing 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.

The study is methodologically sound. It draws on the Global Burden of Disease database (GBD 2023), covers 204 countries between 1990 and 2023, and applies standard, well-executed statistical tools. Its main contribution is to focus specifically on women aged 35 to 49 —the age range in which the biological decline in fertility truly matters— and to project the trend to 2036. The figures are striking in scale: around 53.6 million women in this age group were affected in 2023, with a projection close to 79.6 million by 2036, and a relative shift of the burden from less developed countries towards higher-income ones.

These numbers should nonetheless be read with caution, because the indicator does not measure quite what it appears to. The GBD’s “infertility prevalence” is a modelled figure that depends largely on whether a woman wishes to have children, seeks medical care, and has access to diagnostic services. In other words, it reflects health-care seeking and data-registration quality as much as biology. The clearest proof of this is the implausible disparity between similar countries: Belgium appears with 8,499 cases per 100,000 women and Germany with 2,195; Spain, at 2,226, falls well below the global average (6,907). I do not believe that a Belgian woman is four times more infertile than a German one. It is also worth clarifying what the “infertility rate” means: the study calculates it over all women aged 35–49, not only those trying to conceive, which is what is clinically understood by an infertility rate. Because the denominator is the whole female population in that age band, a mere rise in the number of women attempting pregnancy at older ages inflates the rate even if the per-attempt risk is unchanged; the increase should therefore not be read as a rise in the biological risk of infertility. Two further caveats apply. First, regarding the “burden”: the study expresses it in disability-adjusted life-years (DALYs), but infertility entails no mortality, so this burden consists entirely of a loss of quality of life; put another way, the GBD treats infertility itself as a disability to which it assigns a weight —a debatable value— and it should therefore not be compared with the burden of fatal diseases. Second, the study considers only female infertility and leaves out the male factor, which accounts for a substantial share of cases.

In Spain, the decisive factor is not a new biological epidemic but the postponement of motherhood for socioeconomic reasons. The mean age at first birth is around 33, fertility is among the lowest in the world (1.10 children per woman), and one in ten births is already to mothers aged 40 or over; women themselves cite lack of financial resources, difficulty reconciling work and family life, and fear of the impact on their careers as the main barriers. That is why the most effective lever is social and preventive, not merely clinical: early information about the age-related decline in fertility; measures addressing the structural causes of postponement (housing, job insecurity, work–family balance, and shared responsibility for caregiving); early reproductive assessment in primary care; honest counselling about egg freezing, without presenting it as a guarantee; and more rational, equitable public access to assisted reproduction, without overlooking the male factor. Precision reproductive medicine and genomics also open up a horizon for better characterising the causes and refining individual prognosis.