Falling birth rates have intensified concerns about population ageing, labour shortages and pressure on social security systems worldwide. The United Nations estimates the global fertility rate at 2.25 births per woman, about one child fewer than in 1990. More than half of all countries now record fertility below the replacement level of 2.1 births per woman.
Medical infertility and demographic fertility rates remain distinct issues. However, delayed parenthood and worsening reproductive health may contribute to both trends.
Infertility Rises Among Women Over 35
A new study led by Yuanyuan Du of Chongqing Medical University examined infertility among women aged 35 to 49. Researchers analysed data from 204 countries and territories between 1990 and 2023.
The study found that age-standardised infertility prevalence in this group rose by around 15% over that period. About 53.6 million women aged 35 to 49 experienced infertility in 2023.
The World Health Organization estimates that one in six people of reproductive age experience infertility during their lifetime. The condition can result from female, male or unexplained factors.
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The demographic debate has also attracted public figures. Elon Musk warned in 2021 that “if people stop having children, civilization will crumble.”
Low birth rates can accelerate population ageing and reduce the future workforce. Infertility may also affect women’s careers, lifetime earnings and participation in the labour market.
Cost, Careers and Motherhood Debate
A Swiss Life survey of more than 3,000 people identified several reasons for avoiding or delaying parenthood. Respondents cited limited desire for children, financial costs, time pressures, career conflicts and fears about the world’s future.
Swiss author Nicole Althaus questioned the social change, writing: “The birth rate keeps falling and falling…How on earth did it come to this?”
Althaus argued that some strands of feminism created a more negative image of motherhood. She called this “arguably the saddest chapter in the history of emancipation.”
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Her argument remains contested and represents one interpretation of a complex demographic shift. Economic insecurity, housing costs, childcare shortages and changing personal priorities also influence family decisions.
Althaus traced part of the debate to Simone de Beauvoir. The French philosopher described motherhood as the “enslavement of women by their own species” in her 1949 book The Second Sex.
Pollution and Climate Risks to Fertility
Researchers also warn that climate change and pollutants may harm reproductive health. Extreme heat, wildfire smoke, air pollution and endocrine-disrupting chemicals can affect hormonal signalling and reproductive organs.
Scientists have detected microplastics and nanoplastics in placentas, amniotic fluid and ovarian follicular fluid. Laboratory evidence suggests these particles may damage granulosa cells, which support developing eggs.
Heavy metals, pesticides, PFAS, bisphenols and phthalates may also interfere with ovarian function, implantation and egg quality. Air pollutants have links with menstrual irregularities, poorer embryo quality and reduced chances of conception.
Researchers say folic acid, vitamin D, iodide, omega-3 fatty acids and antioxidants may help under some circumstances. However, evidence varies, and supplements cannot replace medical assessment or policies that restrict toxic chemicals.
