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Women are having fewer children today than in the past globally, but experts say that’s by choice and it doesn’t mean “we are facing a crisis in reproductive health,” as Nicole Shanahan, Robert F. Kennedy Jr.’s running mate, said during her announcement speech. Infertility rates have remained steady during the last decades.
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Since the 1960s, multiple social and cultural changes have led to a significant decline in the average number of children women have.
The global average fertility rate went from 5 children per woman in 1965 to 2.3 in 2021, according to data from the United Nations World Population Prospects presented by Our World in Data. In the U.S., the fertility rate declined from 2.9 to 1.7 in that same time period. The fertility rate measures the average number of children that would be born per woman over her lifetime based on fertility rates across age groups for one year.
Experts and studies point to a combination of factors to explain why women are choosing to have fewer children, including more access to education and to the labor force, the use of contraception, declining rates of child mortality, and the cost of bringing up children.
“[W]omen’s empowerment, the increasing well-being and status of children, technological and economic changes, changing norms, and opportunities for family planning have led to the reduction in the total fertility rate,” reads an analysis by Max Roser, a professor of practice in global data analytics at Oxford University and founder and director of Our World in Data.
But Nicole Shanahan, Robert F. Kennedy Jr.’s choice for his vice presidential running mate, recently left the misleading impression that it’s women’s ability to conceive that is in decline, saying it was part of an “epidemic of chronic disease.”
“I discovered that women’s fertility is in precipitous decline around the world,” she said on March 26, after Kennedy, who’s running for president as an independent, introduced Shanahan as his pick. “We are facing a crisis in reproductive health that is embedded in the larger epidemic of chronic disease.”
The “three main causes” of this “epidemic of chronic disease,” she said, are “toxic substances in our environment,” “electromagnetic pollution” and “pharmaceutical medicine.” Shanahan elaborated on toxic substances, saying they included “endocrine disrupting chemicals in our food, water, and soil, like the pesticide residues, the industrial pollutants, the microplastics, the PFAs, the food additives, and the forever chemicals that have contaminated nearly every human cell.”
In citing “electromagnetic pollution,” Shanahan is referring to electric and magnetic fields coming from multiple appliances and devices, such as cell phones. According to the WHO, “current evidence does not confirm the existence of any health consequences from exposure to low level electromagnetic fields.”
When asked about support for these claims, Kennedy’s campaign told us in an email that Shanahan’s “comments on fertility rates and chronic disease are well documented in science journals that you can investigate on your own.” (As we recently wrote, Shanahan also made a misleading claim about autism during her speech.)
Experts told us these statements on fertility are not supported by science.
“There’s no data out there to say that women’s fertility is precipitately declining,” Eve C. Feinberg, an expert in reproductive endocrinology and infertility at Northwestern University, told us in an interview.
“The birth rate is declining, but I don’t think that the birth rate is declining as a result of a women’s fertility,” Feinberg, who is also a director at large of the American Society for Reproductive Medicine, said. “There are multiple socio-economic factors that go into that birth rate and we think it’s really more intentional decision-making of couples deciding to have fewer children.”
Jennifer Kawwass, endocrinology and infertility expert at the Emory University School of Medicine and director of the Emory Reproductive Center, told us Shanahan’s claims are “presumptions that have not been proven.”
“There is no clear cause effect relationship behind the specific claims. It is true that there are associations between endocrine disruptors and fertility,” she told us in an email, referring to chemicals, such as pesticides, that disrupt the body’s hormones that are part of the endocrine system. “But, the statements are made in a way that is more black and white and more causal than the current evidence suggests.”
Feinberg told us there is a trend among women of having their first child at a later age, which creates a higher rate of infertility among that group, given that age increases the risk of infertility, or not being able to get pregnant after a year of unprotected sex, in women and in men. But infertility rates for younger women remain largely the same, Feinberg said.
“If you were to compare a 28-year-old with a 28-year-old,” now and in the past, she said, “there’s no massive increase in infertility in the younger population.”
A study published in 2022 in Fertility and Sterility supports Feinberg’s statements and shows that the rate of infertility among women in the U.S. has remained roughly the same during the last three decades.
The observational study analyzed data from married and cohabiting women from the National Survey for Family Growth, collected by the National Center for Health Statistics, from 1995 to 2019. Morgan Snow, a medical student at Johns Hopkins University School of Medicine and the study’s first author, told us that previous studies using a similar methodology had found that infertility in women had dropped from 1982 to 2006-2010. One study found 6% of married women ages 15 to 44 were infertile in the latter time frame, down from 8.5% who had trouble conceiving in 1982.
“[O]ur analysis showed that, over the period of 1995 to 2019, infertility among women in the U.S. was no longer on the decline, i.e., was stable and any changes observed were not statistically significant,” she told us in an email.
According to the study results, one of “the most significant determinants of infertility … was the maternal age.” Women aged 40 to 44 who hadn’t given birth before were 11 times more likely to be infertile than younger women. The study also found infertility was more likely in women who hadn’t given birth before, had lower income, had fewer years of education and were non-Hispanic Black. Since sexually transmitted infections are on the rise and contribute to infertility, those who hadn’t received sexual and reproductive health services were also more likely to have difficulty conceiving.
“On a global scale, it is harder to speak to trends,” Snow told us, referring to global infertility rates, because “it is difficult to reconcile different methodological approaches in defining infertility.”
A study that analyzed global patterns and trends in infertility between 1990 and 2010 found “little evidence of changes in infertility over two decades,” except for areas in sub-Saharan Africa and South Asia where infertility went down, not up.
Risk Factors of Infertility
Infertility is a common problem that affects millions of people across the world. A 2023 report by the World Health Organization showed that approximately 1 in 6 people have experienced infertility, globally.
In women, infertility is generally caused by abnormalities of the ovaries, uterus, fallopian tubes and the endocrine system, according to the WHO. In men, the Centers for Disease Control and Prevention says, the condition can be caused by testicular failure and hormonal or genetic disorders that impact the production, mobility and ejection of sperm.
As we said, the risk of women’s infertility increases significantly with age. The CDC says other factors that increase the risk include excessive use of alcohol, smoking, being over- or underweight or obese, and excessive stress. Similarly, in men, the scientific literature shows that age, obesity, excessive use of alcohol and smoking can increase the risk of infertility. Other factors include exposure to radiation and some chemotherapy treatments, exposure to heat in the testes such as in saunas and hot tubs, and the use of certain medications such as testosterone and anabolic steroids.
If infertility was caused by any of the factors that Shanahan mentioned, Feinberg told us, there would be trends and patterns among different populations across the world that could be more exposed to the toxic substances Shanahan cited. But the WHO report, which analyzed 133 studies from 1990 to 2021, didn’t find substantial variations in infertility prevalence between geographic regions or countries.
Although there are studies that have shown associations with exposure to certain toxic substances, such as endocrine disruptors, and infertility, including in men, Feinberg said they “don’t show actual proof of causation.”
“With regard to the epidemic of chronic disease, I mean, probably the biggest disease that attacks fertility is obesity,” Feinberg said. “And so I would say we are facing a crisis with regard to obesity as it pertains to fertility and as it pertains to complications and pregnancy. But you know, with regard to like other types of chronic diseases, medications, pharmaceuticals, environment, we’re simply not seeing that to be the case.”
Editor’s note: SciCheck’s articles providing accurate health information and correcting health misinformation are made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over FactCheck.org’s editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation.
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