Concerns about a potential long-term population decline are gaining traction worldwide as fertility rates fall among both women and men. That trend has drawn the attention of politicians, policymakers, and public figures alike.

The issue has also entered the public conversation through billionaire Elon Musk, who in 2021 warned at an economic summit that “if people stop having children, civilization will crumble.” More recently, the Swiss newspaper Neue Zürcher Zeitung (NZZ) — one of Switzerland’s leading quality daily newspapers — highlighted the broader demographic concern, noting that it is fueling debate over the future of population growth.

Now, a recent study may add to those worries. Investigators led by Yuanyuan Du of Women and Children’s Hospital, Chongqing Medical University, in Chongqing, China, reported that the prevalence of infertility among women aged 35-49 years, an age range often considered advanced reproductive age, has increased by about 15% since 1990.

A Social and Economic Problem

In light of the global population’s aging, infertility among women of advanced reproductive age has become a serious public health problem with significant economic implications for women, families, and healthcare systems, according to the authors of the recent study. Economic analyses have shown that limitations caused by infertility impair women’s labor force participation, their career trajectories, and their lifetime earning potential, ultimately reducing overall economic productivity. At the macroeconomic level, a persistently low birth rate accelerates population aging, places a strain on social security systems, and hinders long-term economic growth.

A team of gynecologists led by Maren Goeckenjan-Festag, MD, University Hospital Carl Gustav Carus Dresden, Dresden, Germany, also emphasized in a journal article on the influence of environmental factors on female fertility that reduced female and male fertility ranks among the world’s top health priorities, alongside cardiovascular and oncologic diseases.

Lack of Desire to Have Children, Fear of the Future, Feminism

What are the causes of declining birth rates? In a study by the insurance company Swiss Life, more than 3000 people were surveyed about their wishes and reasons regarding having children, as recently reported by the NZZ. The most frequently cited reasons for deciding against having children were a lack of desire to have children, the fact that children require too much time and money, fears about the state of the world, or the difficulty of balancing a career with family life. Those who do want children are postponing having them until later in life.

Swiss author Nicole Althaus has argued that feminism has also played a role in some women’s decision to remain childless.

“The birth rate keeps falling and falling…How on earth did it come to this?” Althaus wrote, suggesting that in many women’s lives — whether they are emancipated part-time mothers, modern “tradwives,” or childless by choice — the decision to have children is increasingly treated as something that must be explained.

She said feminism has contributed both to the pressure women feel to justify their choices and to a more negative view of motherhood. In her view, this is “arguably the saddest chapter in the history of emancipation” because women’s liberation has, in some cases, come at the expense of motherhood.

Ever since French philosopher Simone de Beauvoir reframed motherhood in her 1949 landmark work The Second Sex — arguing that it could function as a trap for women and describing it as the “enslavement of women by their own species” — the family has often been cast as a central site of female oppression.

Under that framework, the argument goes, a woman who becomes a mother cannot be fully free. According to Althaus, later generations of feminists did little to challenge that link between motherhood and lack of autonomy.

Writing in NZZ am Sonntag, the Sunday edition of NZZ, Althaus said that many of the movement’s best-known figures — including de Beauvoir, US feminist scholar Kate Millett, German journalist and feminist Alice Schwarzer, and gender theorist Judith Butler — came to this conclusion and remained childless.

Climate Change and Fertility

Environmental factors that impair fertility are also said to have contributed to the declining birth rates. Studies have shown that female fertility is negatively affected by climate change and exposure to pollutants, report Maren Goeckenjan-Festag and her colleagues Sina Lehmann, specialist for gynecology, Health for Future, Dresden and Annette Hasenburg, Johannes Gutenberg University Mainz, Mainz, Germany.

Globally, more frequent periods of extreme heat and cold are increasingly affecting daily life, nutrition, water access, and fertility.

Researchers say that environmental exposures — including chemical pollutants, air pollution, endocrine-disrupting compounds, and radiation — may interfere with the menstrual cycle, follicular development, and the quality of eggs and embryos.

Of particular concern are persistent pollutants, such as microplastics, nanoplastics, and organochlorine compounds, which may have lasting effects on fertility and could also influence future generations.

The finding that multiple environmental pollutants have been detected in follicular fluid, the fluid surrounding the developing egg in the ovary, is especially troubling, investigators said.

Climate change is a major threat to the world’s population and is attributable to global warming caused by human activities, as a research team led by Anna Claire G. Fernandez, University of California, San Francisco, recently emphasized in the journal Endocrine Reviews. It has direct and indirect effects on human health and well-being worldwide, with particularly vulnerable population groups being disproportionately affected, including women, pregnant women, unborn children, children, older adults, indigenous peoples, people with disabilities, people with preexisting and/or chronic conditions, as well as low-income and ethnic minority groups.

Climate change may affect reproductive health both directly and indirectly, researchers say.

According to Goeckenjan-Festag and colleagues, direct effects may involve hormonal changes, cellular injury, and impacts on reproductive organs. Indirect effects include greater exposure to fine particulate matter from wildfires, as well as stress and a higher risk for infection.

The authors also noted that extreme weather events and natural disasters can worsen existing social and structural inequalities, leaving some populations even more vulnerable, particularly those with limited access to food, safe drinking water, and medical care.

Because of their social position, women and children are among the groups most affected by climate-related health risks. Limited access to care can in turn raise maternal and neonatal morbidity and mortality, the researchers wrote in Nature Medicine.

Geopolitical crises and wars also exacerbate the physical and psychological strain on the population, both through direct threats and through additional environmental pollution from harmful substances. Progressive global urbanization could improve access to medical care, but at the same time exacerbate health risks caused by climate change and pollution in metropolitan areas. According to UN estimates, 55% of the world’s population now lives in cities.

Environmental Pollutants and Female Fertility

According to the gynecologists, another relevant current issue for female fertility is exposure to microplastics and nanoplastics, endocrine disruptors, persistent chemical pollutants, and air pollutants.

Microplastic and nanoplastic particles are now detectable worldwide, and exposure can occur through food, inhalation, and even the skin. Researchers also say these particles can enter bodily secretions and organs.

They have been detected not only in the placenta and amniotic fluid but also in follicular fluid. Of particular concern for fertility are findings suggesting damage to granulosa cells, which support egg development, and disruption of follicular maturation, according to a report in NanoImpact, a peer-reviewed journal focused on nanoscience and its biological effects.

Heavy metals may impair fertility through several mechanisms, including DNA damage,oxidative stress, apoptosis, interactions with other ions, and hormonal disruption — that is, interference with the body’s natural endocrine system by outside chemical substances, according to Reproductive Toxicology.

Cadmium, in particular, is a toxic heavy metal that can accumulate in soil and water and, after ingestion, build up in the human body.

Endocrine disruptors are substances or mixtures that alter the endocrine system and could cause adverse effects in an intact organism, its offspring, a population, or a subpopulation. Substances relevant to fertility include persistent organic pollutants such as dichlorodiphenyltrichloroethane (DDT), heptachlor epoxide, and polychlorinated biphenyls, which should no longer be used. Bisphenols, phthalates, parabens, and PFAS, as well as pesticides and dioxins, also act as endocrine disruptors. In addition to direct agonistic or antagonistic effects on the estrogen receptor, endocrine disruptors may influence the gonadal axis, ovarian function, implantation, and reproductive behavior (Life; MDPI).

Air Pollutants: According to the world health organization, it is estimated that nearly the entire world population breathes air that exceeds air quality guidelines. A meta-analysis found that higher exposure to air pollutants was significantly associated with poorer embryo quality, lower fecundity — the probability of conception per menstrual cycle — and reduced chances of implantation.

According to the authors, several factors were especially important in this relationship:

• particulate matter from combustion processes, 
• nitrogen oxides from traffic, heating, and energy production, and 
• carbon monoxide. 

Further studies have confirmed that exposure to fine particulate matter with a particle size of approximately 2.5 µm in diameter is associated with menstrual cycle irregularities, impaired egg quality, reduced embryo quality, and a diminished ovarian reserve according to the Journal of Gynecology, Obstetrics, and Human Reproduction.

Radiation: Ionizing and nonionizing radiation can impair fertility depending on the type and dose, as well as the age at the time of exposure. Naturally occurring radon accounts for the majority of natural ionizing radiation. The total dose is particularly relevant for health risk assessment. However, it has not yet been conclusively determined whether non-ionizing, low-energy radiation — such as that from cell phones, computers, or radar — affects female fertility.

Prevention With Vitamin D and Omega-3 Fatty Acids

According to Goeckenjan-Festag and her colleagues, the findings on the effects of pollutants on fertility can be used in gynecologic counseling. For example, a meta-analysis on interactions between dietary supplements and endocrine disruptors suggests that iodide, folic acid, vitamin D, and substances with antioxidant effects may partially offset negative effects on fertility. Adequate folic acid supplementation has also been described as a possible preventive intervention for pesticide exposure, such as from DDT.

Since oxidative stress is considered a key mechanism in the impairment of egg quality, in addition to a healthy diet and optimizing living conditions, antioxidant dietary supplements such as omega-3 fatty acids could be recommended prior to planned pregnancies.

In addition to individual counseling, gynecologists could advocate for policy and systemic measures, such as regulations to restrict toxic chemicals.

This story was translated from Univadis Germany, part of the Medscape Professional Network.